intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 2838 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Lib/pydoc.py b/contrib/tools/python3/src/Lib/pydoc.py
new file mode 100644
index 0000000000..4f9d227ff4
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/pydoc.py
@@ -0,0 +1,2838 @@
+#!/usr/bin/env python3
+"""Generate Python documentation in HTML or text for interactive use.
+
+At the Python interactive prompt, calling help(thing) on a Python object
+documents the object, and calling help() starts up an interactive
+help session.
+
+Or, at the shell command line outside of Python:
+
+Run "pydoc <name>" to show documentation on something.  <name> may be
+the name of a function, module, package, or a dotted reference to a
+class or function within a module or module in a package.  If the
+argument contains a path segment delimiter (e.g. slash on Unix,
+backslash on Windows) it is treated as the path to a Python source file.
+
+Run "pydoc -k <keyword>" to search for a keyword in the synopsis lines
+of all available modules.
+
+Run "pydoc -n <hostname>" to start an HTTP server with the given
+hostname (default: localhost) on the local machine.
+
+Run "pydoc -p <port>" to start an HTTP server on the given port on the
+local machine.  Port number 0 can be used to get an arbitrary unused port.
+
+Run "pydoc -b" to start an HTTP server on an arbitrary unused port and
+open a Web browser to interactively browse documentation.  Combine with
+the -n and -p options to control the hostname and port used.
+
+Run "pydoc -w <name>" to write out the HTML documentation for a module
+to a file named "<name>.html".
+
+Module docs for core modules are assumed to be in
+
+    https://docs.python.org/X.Y/library/
+
+This can be overridden by setting the PYTHONDOCS environment variable
+to a different URL or to a local directory containing the Library
+Reference Manual pages.
+"""
+__all__ = ['help']
+__author__ = "Ka-Ping Yee <ping@lfw.org>"
+__date__ = "26 February 2001"
+
+__credits__ = """Guido van Rossum, for an excellent programming language.
+Tommy Burnette, the original creator of manpy.
+Paul Prescod, for all his work on onlinehelp.
+Richard Chamberlain, for the first implementation of textdoc.
+"""
+
+# Known bugs that can't be fixed here:
+#   - synopsis() cannot be prevented from clobbering existing
+#     loaded modules.
+#   - If the __file__ attribute on a module is a relative path and
+#     the current directory is changed with os.chdir(), an incorrect
+#     path will be displayed.
+
+import builtins
+import importlib._bootstrap
+import importlib._bootstrap_external
+import importlib.machinery
+import importlib.util
+import inspect
+import io
+import os
+import pkgutil
+import platform
+import re
+import sys
+import sysconfig
+import time
+import tokenize
+import urllib.parse
+import warnings
+from collections import deque
+from reprlib import Repr
+from traceback import format_exception_only
+
+
+# --------------------------------------------------------- common routines
+
+def pathdirs():
+    """Convert sys.path into a list of absolute, existing, unique paths."""
+    dirs = []
+    normdirs = []
+    for dir in sys.path:
+        dir = os.path.abspath(dir or '.')
+        normdir = os.path.normcase(dir)
+        if normdir not in normdirs and os.path.isdir(dir):
+            dirs.append(dir)
+            normdirs.append(normdir)
+    return dirs
+
+def _findclass(func):
+    cls = sys.modules.get(func.__module__)
+    if cls is None:
+        return None
+    for name in func.__qualname__.split('.')[:-1]:
+        cls = getattr(cls, name)
+    if not inspect.isclass(cls):
+        return None
+    return cls
+
+def _finddoc(obj):
+    if inspect.ismethod(obj):
+        name = obj.__func__.__name__
+        self = obj.__self__
+        if (inspect.isclass(self) and
+            getattr(getattr(self, name, None), '__func__') is obj.__func__):
+            # classmethod
+            cls = self
+        else:
+            cls = self.__class__
+    elif inspect.isfunction(obj):
+        name = obj.__name__
+        cls = _findclass(obj)
+        if cls is None or getattr(cls, name) is not obj:
+            return None
+    elif inspect.isbuiltin(obj):
+        name = obj.__name__
+        self = obj.__self__
+        if (inspect.isclass(self) and
+            self.__qualname__ + '.' + name == obj.__qualname__):
+            # classmethod
+            cls = self
+        else:
+            cls = self.__class__
+    # Should be tested before isdatadescriptor().
+    elif isinstance(obj, property):
+        func = obj.fget
+        name = func.__name__
+        cls = _findclass(func)
+        if cls is None or getattr(cls, name) is not obj:
+            return None
+    elif inspect.ismethoddescriptor(obj) or inspect.isdatadescriptor(obj):
+        name = obj.__name__
+        cls = obj.__objclass__
+        if getattr(cls, name) is not obj:
+            return None
+        if inspect.ismemberdescriptor(obj):
+            slots = getattr(cls, '__slots__', None)
+            if isinstance(slots, dict) and name in slots:
+                return slots[name]
+    else:
+        return None
+    for base in cls.__mro__:
+        try:
+            doc = _getowndoc(getattr(base, name))
+        except AttributeError:
+            continue
+        if doc is not None:
+            return doc
+    return None
+
+def _getowndoc(obj):
+    """Get the documentation string for an object if it is not
+    inherited from its class."""
+    try:
+        doc = object.__getattribute__(obj, '__doc__')
+        if doc is None:
+            return None
+        if obj is not type:
+            typedoc = type(obj).__doc__
+            if isinstance(typedoc, str) and typedoc == doc:
+                return None
+        return doc
+    except AttributeError:
+        return None
+
+def _getdoc(object):
+    """Get the documentation string for an object.
+
+    All tabs are expanded to spaces.  To clean up docstrings that are
+    indented to line up with blocks of code, any whitespace than can be
+    uniformly removed from the second line onwards is removed."""
+    doc = _getowndoc(object)
+    if doc is None:
+        try:
+            doc = _finddoc(object)
+        except (AttributeError, TypeError):
+            return None
+    if not isinstance(doc, str):
+        return None
+    return inspect.cleandoc(doc)
+
+def getdoc(object):
+    """Get the doc string or comments for an object."""
+    result = _getdoc(object) or inspect.getcomments(object)
+    return result and re.sub('^ *\n', '', result.rstrip()) or ''
+
+def splitdoc(doc):
+    """Split a doc string into a synopsis line (if any) and the rest."""
+    lines = doc.strip().split('\n')
+    if len(lines) == 1:
+        return lines[0], ''
+    elif len(lines) >= 2 and not lines[1].rstrip():
+        return lines[0], '\n'.join(lines[2:])
+    return '', '\n'.join(lines)
+
+def classname(object, modname):
+    """Get a class name and qualify it with a module name if necessary."""
+    name = object.__name__
+    if object.__module__ != modname:
+        name = object.__module__ + '.' + name
+    return name
+
+def isdata(object):
+    """Check if an object is of a type that probably means it's data."""
+    return not (inspect.ismodule(object) or inspect.isclass(object) or
+                inspect.isroutine(object) or inspect.isframe(object) or
+                inspect.istraceback(object) or inspect.iscode(object))
+
+def replace(text, *pairs):
+    """Do a series of global replacements on a string."""
+    while pairs:
+        text = pairs[1].join(text.split(pairs[0]))
+        pairs = pairs[2:]
+    return text
+
+def cram(text, maxlen):
+    """Omit part of a string if needed to make it fit in a maximum length."""
+    if len(text) > maxlen:
+        pre = max(0, (maxlen-3)//2)
+        post = max(0, maxlen-3-pre)
+        return text[:pre] + '...' + text[len(text)-post:]
+    return text
+
+_re_stripid = re.compile(r' at 0x[0-9a-f]{6,16}(>+)$', re.IGNORECASE)
+def stripid(text):
+    """Remove the hexadecimal id from a Python object representation."""
+    # The behaviour of %p is implementation-dependent in terms of case.
+    return _re_stripid.sub(r'\1', text)
+
+def _is_bound_method(fn):
+    """
+    Returns True if fn is a bound method, regardless of whether
+    fn was implemented in Python or in C.
+    """
+    if inspect.ismethod(fn):
+        return True
+    if inspect.isbuiltin(fn):
+        self = getattr(fn, '__self__', None)
+        return not (inspect.ismodule(self) or (self is None))
+    return False
+
+
+def allmethods(cl):
+    methods = {}
+    for key, value in inspect.getmembers(cl, inspect.isroutine):
+        methods[key] = 1
+    for base in cl.__bases__:
+        methods.update(allmethods(base)) # all your base are belong to us
+    for key in methods.keys():
+        methods[key] = getattr(cl, key)
+    return methods
+
+def _split_list(s, predicate):
+    """Split sequence s via predicate, and return pair ([true], [false]).
+
+    The return value is a 2-tuple of lists,
+        ([x for x in s if predicate(x)],
+         [x for x in s if not predicate(x)])
+    """
+
+    yes = []
+    no = []
+    for x in s:
+        if predicate(x):
+            yes.append(x)
+        else:
+            no.append(x)
+    return yes, no
+
+def visiblename(name, all=None, obj=None):
+    """Decide whether to show documentation on a variable."""
+    # Certain special names are redundant or internal.
+    # XXX Remove __initializing__?
+    if name in {'__author__', '__builtins__', '__cached__', '__credits__',
+                '__date__', '__doc__', '__file__', '__spec__',
+                '__loader__', '__module__', '__name__', '__package__',
+                '__path__', '__qualname__', '__slots__', '__version__'}:
+        return 0
+    # Private names are hidden, but special names are displayed.
+    if name.startswith('__') and name.endswith('__'): return 1
+    # Namedtuples have public fields and methods with a single leading underscore
+    if name.startswith('_') and hasattr(obj, '_fields'):
+        return True
+    if all is not None:
+        # only document that which the programmer exported in __all__
+        return name in all
+    else:
+        return not name.startswith('_')
+
+def classify_class_attrs(object):
+    """Wrap inspect.classify_class_attrs, with fixup for data descriptors."""
+    results = []
+    for (name, kind, cls, value) in inspect.classify_class_attrs(object):
+        if inspect.isdatadescriptor(value):
+            kind = 'data descriptor'
+            if isinstance(value, property) and value.fset is None:
+                kind = 'readonly property'
+        results.append((name, kind, cls, value))
+    return results
+
+def sort_attributes(attrs, object):
+    'Sort the attrs list in-place by _fields and then alphabetically by name'
+    # This allows data descriptors to be ordered according
+    # to a _fields attribute if present.
+    fields = getattr(object, '_fields', [])
+    try:
+        field_order = {name : i-len(fields) for (i, name) in enumerate(fields)}
+    except TypeError:
+        field_order = {}
+    keyfunc = lambda attr: (field_order.get(attr[0], 0), attr[0])
+    attrs.sort(key=keyfunc)
+
+# ----------------------------------------------------- module manipulation
+
+def ispackage(path):
+    """Guess whether a path refers to a package directory."""
+    if os.path.isdir(path):
+        for ext in ('.py', '.pyc'):
+            if os.path.isfile(os.path.join(path, '__init__' + ext)):
+                return True
+    return False
+
+def source_synopsis(file):
+    line = file.readline()
+    while line[:1] == '#' or not line.strip():
+        line = file.readline()
+        if not line: break
+    line = line.strip()
+    if line[:4] == 'r"""': line = line[1:]
+    if line[:3] == '"""':
+        line = line[3:]
+        if line[-1:] == '\\': line = line[:-1]
+        while not line.strip():
+            line = file.readline()
+            if not line: break
+        result = line.split('"""')[0].strip()
+    else: result = None
+    return result
+
+def synopsis(filename, cache={}):
+    """Get the one-line summary out of a module file."""
+    mtime = os.stat(filename).st_mtime
+    lastupdate, result = cache.get(filename, (None, None))
+    if lastupdate is None or lastupdate < mtime:
+        # Look for binary suffixes first, falling back to source.
+        if filename.endswith(tuple(importlib.machinery.BYTECODE_SUFFIXES)):
+            loader_cls = importlib.machinery.SourcelessFileLoader
+        elif filename.endswith(tuple(importlib.machinery.EXTENSION_SUFFIXES)):
+            loader_cls = importlib.machinery.ExtensionFileLoader
+        else:
+            loader_cls = None
+        # Now handle the choice.
+        if loader_cls is None:
+            # Must be a source file.
+            try:
+                file = tokenize.open(filename)
+            except OSError:
+                # module can't be opened, so skip it
+                return None
+            # text modules can be directly examined
+            with file:
+                result = source_synopsis(file)
+        else:
+            # Must be a binary module, which has to be imported.
+            loader = loader_cls('__temp__', filename)
+            # XXX We probably don't need to pass in the loader here.
+            spec = importlib.util.spec_from_file_location('__temp__', filename,
+                                                          loader=loader)
+            try:
+                module = importlib._bootstrap._load(spec)
+            except:
+                return None
+            del sys.modules['__temp__']
+            result = module.__doc__.splitlines()[0] if module.__doc__ else None
+        # Cache the result.
+        cache[filename] = (mtime, result)
+    return result
+
+class ErrorDuringImport(Exception):
+    """Errors that occurred while trying to import something to document it."""
+    def __init__(self, filename, exc_info):
+        self.filename = filename
+        self.exc, self.value, self.tb = exc_info
+
+    def __str__(self):
+        exc = self.exc.__name__
+        return 'problem in %s - %s: %s' % (self.filename, exc, self.value)
+
+def importfile(path):
+    """Import a Python source file or compiled file given its path."""
+    magic = importlib.util.MAGIC_NUMBER
+    with open(path, 'rb') as file:
+        is_bytecode = magic == file.read(len(magic))
+    filename = os.path.basename(path)
+    name, ext = os.path.splitext(filename)
+    if is_bytecode:
+        loader = importlib._bootstrap_external.SourcelessFileLoader(name, path)
+    else:
+        loader = importlib._bootstrap_external.SourceFileLoader(name, path)
+    # XXX We probably don't need to pass in the loader here.
+    spec = importlib.util.spec_from_file_location(name, path, loader=loader)
+    try:
+        return importlib._bootstrap._load(spec)
+    except:
+        raise ErrorDuringImport(path, sys.exc_info())
+
+def safeimport(path, forceload=0, cache={}):
+    """Import a module; handle errors; return None if the module isn't found.
+
+    If the module *is* found but an exception occurs, it's wrapped in an
+    ErrorDuringImport exception and reraised.  Unlike __import__, if a
+    package path is specified, the module at the end of the path is returned,
+    not the package at the beginning.  If the optional 'forceload' argument
+    is 1, we reload the module from disk (unless it's a dynamic extension)."""
+    try:
+        # If forceload is 1 and the module has been previously loaded from
+        # disk, we always have to reload the module.  Checking the file's
+        # mtime isn't good enough (e.g. the module could contain a class
+        # that inherits from another module that has changed).
+        if forceload and path in sys.modules:
+            if path not in sys.builtin_module_names:
+                # Remove the module from sys.modules and re-import to try
+                # and avoid problems with partially loaded modules.
+                # Also remove any submodules because they won't appear
+                # in the newly loaded module's namespace if they're already
+                # in sys.modules.
+                subs = [m for m in sys.modules if m.startswith(path + '.')]
+                for key in [path] + subs:
+                    # Prevent garbage collection.
+                    cache[key] = sys.modules[key]
+                    del sys.modules[key]
+        module = __import__(path)
+    except:
+        # Did the error occur before or after the module was found?
+        (exc, value, tb) = info = sys.exc_info()
+        if path in sys.modules:
+            # An error occurred while executing the imported module.
+            raise ErrorDuringImport(sys.modules[path].__file__, info)
+        elif exc is SyntaxError:
+            # A SyntaxError occurred before we could execute the module.
+            raise ErrorDuringImport(value.filename, info)
+        elif issubclass(exc, ImportError) and value.name == path:
+            # No such module in the path.
+            return None
+        else:
+            # Some other error occurred during the importing process.
+            raise ErrorDuringImport(path, sys.exc_info())
+    for part in path.split('.')[1:]:
+        try: module = getattr(module, part)
+        except AttributeError: return None
+    return module
+
+# ---------------------------------------------------- formatter base class
+
+class Doc:
+
+    PYTHONDOCS = os.environ.get("PYTHONDOCS",
+                                "https://docs.python.org/%d.%d/library"
+                                % sys.version_info[:2])
+
+    def document(self, object, name=None, *args):
+        """Generate documentation for an object."""
+        args = (object, name) + args
+        # 'try' clause is to attempt to handle the possibility that inspect
+        # identifies something in a way that pydoc itself has issues handling;
+        # think 'super' and how it is a descriptor (which raises the exception
+        # by lacking a __name__ attribute) and an instance.
+        try:
+            if inspect.ismodule(object): return self.docmodule(*args)
+            if inspect.isclass(object): return self.docclass(*args)
+            if inspect.isroutine(object): return self.docroutine(*args)
+        except AttributeError:
+            pass
+        if inspect.isdatadescriptor(object): return self.docdata(*args)
+        return self.docother(*args)
+
+    def fail(self, object, name=None, *args):
+        """Raise an exception for unimplemented types."""
+        message = "don't know how to document object%s of type %s" % (
+            name and ' ' + repr(name), type(object).__name__)
+        raise TypeError(message)
+
+    docmodule = docclass = docroutine = docother = docproperty = docdata = fail
+
+    def getdocloc(self, object, basedir=sysconfig.get_path('stdlib')):
+        """Return the location of module docs or None"""
+
+        try:
+            file = inspect.getabsfile(object)
+        except TypeError:
+            file = '(built-in)'
+
+        docloc = os.environ.get("PYTHONDOCS", self.PYTHONDOCS)
+
+        basedir = os.path.normcase(basedir)
+        if (isinstance(object, type(os)) and
+            (object.__name__ in ('errno', 'exceptions', 'gc', 'imp',
+                                 'marshal', 'posix', 'signal', 'sys',
+                                 '_thread', 'zipimport') or
+             (file.startswith(basedir) and
+              not file.startswith(os.path.join(basedir, 'site-packages')))) and
+            object.__name__ not in ('xml.etree', 'test.pydoc_mod')):
+            if docloc.startswith(("http://", "https://")):
+                docloc = "%s/%s" % (docloc.rstrip("/"), object.__name__.lower())
+            else:
+                docloc = os.path.join(docloc, object.__name__.lower() + ".html")
+        else:
+            docloc = None
+        return docloc
+
+# -------------------------------------------- HTML documentation generator
+
+class HTMLRepr(Repr):
+    """Class for safely making an HTML representation of a Python object."""
+    def __init__(self):
+        Repr.__init__(self)
+        self.maxlist = self.maxtuple = 20
+        self.maxdict = 10
+        self.maxstring = self.maxother = 100
+
+    def escape(self, text):
+        return replace(text, '&', '&amp;', '<', '&lt;', '>', '&gt;')
+
+    def repr(self, object):
+        return Repr.repr(self, object)
+
+    def repr1(self, x, level):
+        if hasattr(type(x), '__name__'):
+            methodname = 'repr_' + '_'.join(type(x).__name__.split())
+            if hasattr(self, methodname):
+                return getattr(self, methodname)(x, level)
+        return self.escape(cram(stripid(repr(x)), self.maxother))
+
+    def repr_string(self, x, level):
+        test = cram(x, self.maxstring)
+        testrepr = repr(test)
+        if '\\' in test and '\\' not in replace(testrepr, r'\\', ''):
+            # Backslashes are only literal in the string and are never
+            # needed to make any special characters, so show a raw string.
+            return 'r' + testrepr[0] + self.escape(test) + testrepr[0]
+        return re.sub(r'((\\[\\abfnrtv\'"]|\\[0-9]..|\\x..|\\u....)+)',
+                      r'<font color="#c040c0">\1</font>',
+                      self.escape(testrepr))
+
+    repr_str = repr_string
+
+    def repr_instance(self, x, level):
+        try:
+            return self.escape(cram(stripid(repr(x)), self.maxstring))
+        except:
+            return self.escape('<%s instance>' % x.__class__.__name__)
+
+    repr_unicode = repr_string
+
+class HTMLDoc(Doc):
+    """Formatter class for HTML documentation."""
+
+    # ------------------------------------------- HTML formatting utilities
+
+    _repr_instance = HTMLRepr()
+    repr = _repr_instance.repr
+    escape = _repr_instance.escape
+
+    def page(self, title, contents):
+        """Format an HTML page."""
+        return '''\
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
+<html><head><title>Python: %s</title>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+</head><body bgcolor="#f0f0f8">
+%s
+</body></html>''' % (title, contents)
+
+    def heading(self, title, fgcol, bgcol, extras=''):
+        """Format a page heading."""
+        return '''
+<table width="100%%" cellspacing=0 cellpadding=2 border=0 summary="heading">
+<tr bgcolor="%s">
+<td valign=bottom>&nbsp;<br>
+<font color="%s" face="helvetica, arial">&nbsp;<br>%s</font></td
+><td align=right valign=bottom
+><font color="%s" face="helvetica, arial">%s</font></td></tr></table>
+    ''' % (bgcol, fgcol, title, fgcol, extras or '&nbsp;')
+
+    def section(self, title, fgcol, bgcol, contents, width=6,
+                prelude='', marginalia=None, gap='&nbsp;'):
+        """Format a section with a heading."""
+        if marginalia is None:
+            marginalia = '<tt>' + '&nbsp;' * width + '</tt>'
+        result = '''<p>
+<table width="100%%" cellspacing=0 cellpadding=2 border=0 summary="section">
+<tr bgcolor="%s">
+<td colspan=3 valign=bottom>&nbsp;<br>
+<font color="%s" face="helvetica, arial">%s</font></td></tr>
+    ''' % (bgcol, fgcol, title)
+        if prelude:
+            result = result + '''
+<tr bgcolor="%s"><td rowspan=2>%s</td>
+<td colspan=2>%s</td></tr>
+<tr><td>%s</td>''' % (bgcol, marginalia, prelude, gap)
+        else:
+            result = result + '''
+<tr><td bgcolor="%s">%s</td><td>%s</td>''' % (bgcol, marginalia, gap)
+
+        return result + '\n<td width="100%%">%s</td></tr></table>' % contents
+
+    def bigsection(self, title, *args):
+        """Format a section with a big heading."""
+        title = '<big><strong>%s</strong></big>' % title
+        return self.section(title, *args)
+
+    def preformat(self, text):
+        """Format literal preformatted text."""
+        text = self.escape(text.expandtabs())
+        return replace(text, '\n\n', '\n \n', '\n\n', '\n \n',
+                             ' ', '&nbsp;', '\n', '<br>\n')
+
+    def multicolumn(self, list, format, cols=4):
+        """Format a list of items into a multi-column list."""
+        result = ''
+        rows = (len(list)+cols-1)//cols
+        for col in range(cols):
+            result = result + '<td width="%d%%" valign=top>' % (100//cols)
+            for i in range(rows*col, rows*col+rows):
+                if i < len(list):
+                    result = result + format(list[i]) + '<br>\n'
+            result = result + '</td>'
+        return '<table width="100%%" summary="list"><tr>%s</tr></table>' % result
+
+    def grey(self, text): return '<font color="#909090">%s</font>' % text
+
+    def namelink(self, name, *dicts):
+        """Make a link for an identifier, given name-to-URL mappings."""
+        for dict in dicts:
+            if name in dict:
+                return '<a href="%s">%s</a>' % (dict[name], name)
+        return name
+
+    def classlink(self, object, modname):
+        """Make a link for a class."""
+        name, module = object.__name__, sys.modules.get(object.__module__)
+        if hasattr(module, name) and getattr(module, name) is object:
+            return '<a href="%s.html#%s">%s</a>' % (
+                module.__name__, name, classname(object, modname))
+        return classname(object, modname)
+
+    def modulelink(self, object):
+        """Make a link for a module."""
+        return '<a href="%s.html">%s</a>' % (object.__name__, object.__name__)
+
+    def modpkglink(self, modpkginfo):
+        """Make a link for a module or package to display in an index."""
+        name, path, ispackage, shadowed = modpkginfo
+        if shadowed:
+            return self.grey(name)
+        if path:
+            url = '%s.%s.html' % (path, name)
+        else:
+            url = '%s.html' % name
+        if ispackage:
+            text = '<strong>%s</strong>&nbsp;(package)' % name
+        else:
+            text = name
+        return '<a href="%s">%s</a>' % (url, text)
+
+    def filelink(self, url, path):
+        """Make a link to source file."""
+        return '<a href="file:%s">%s</a>' % (url, path)
+
+    def markup(self, text, escape=None, funcs={}, classes={}, methods={}):
+        """Mark up some plain text, given a context of symbols to look for.
+        Each context dictionary maps object names to anchor names."""
+        escape = escape or self.escape
+        results = []
+        here = 0
+        pattern = re.compile(r'\b((http|https|ftp)://\S+[\w/]|'
+                                r'RFC[- ]?(\d+)|'
+                                r'PEP[- ]?(\d+)|'
+                                r'(self\.)?(\w+))')
+        while True:
+            match = pattern.search(text, here)
+            if not match: break
+            start, end = match.span()
+            results.append(escape(text[here:start]))
+
+            all, scheme, rfc, pep, selfdot, name = match.groups()
+            if scheme:
+                url = escape(all).replace('"', '&quot;')
+                results.append('<a href="%s">%s</a>' % (url, url))
+            elif rfc:
+                url = 'http://www.rfc-editor.org/rfc/rfc%d.txt' % int(rfc)
+                results.append('<a href="%s">%s</a>' % (url, escape(all)))
+            elif pep:
+                url = 'https://www.python.org/dev/peps/pep-%04d/' % int(pep)
+                results.append('<a href="%s">%s</a>' % (url, escape(all)))
+            elif selfdot:
+                # Create a link for methods like 'self.method(...)'
+                # and use <strong> for attributes like 'self.attr'
+                if text[end:end+1] == '(':
+                    results.append('self.' + self.namelink(name, methods))
+                else:
+                    results.append('self.<strong>%s</strong>' % name)
+            elif text[end:end+1] == '(':
+                results.append(self.namelink(name, methods, funcs, classes))
+            else:
+                results.append(self.namelink(name, classes))
+            here = end
+        results.append(escape(text[here:]))
+        return ''.join(results)
+
+    # ---------------------------------------------- type-specific routines
+
+    def formattree(self, tree, modname, parent=None):
+        """Produce HTML for a class tree as given by inspect.getclasstree()."""
+        result = ''
+        for entry in tree:
+            if type(entry) is type(()):
+                c, bases = entry
+                result = result + '<dt><font face="helvetica, arial">'
+                result = result + self.classlink(c, modname)
+                if bases and bases != (parent,):
+                    parents = []
+                    for base in bases:
+                        parents.append(self.classlink(base, modname))
+                    result = result + '(' + ', '.join(parents) + ')'
+                result = result + '\n</font></dt>'
+            elif type(entry) is type([]):
+                result = result + '<dd>\n%s</dd>\n' % self.formattree(
+                    entry, modname, c)
+        return '<dl>\n%s</dl>\n' % result
+
+    def docmodule(self, object, name=None, mod=None, *ignored):
+        """Produce HTML documentation for a module object."""
+        name = object.__name__ # ignore the passed-in name
+        try:
+            all = object.__all__
+        except AttributeError:
+            all = None
+        parts = name.split('.')
+        links = []
+        for i in range(len(parts)-1):
+            links.append(
+                '<a href="%s.html"><font color="#ffffff">%s</font></a>' %
+                ('.'.join(parts[:i+1]), parts[i]))
+        linkedname = '.'.join(links + parts[-1:])
+        head = '<big><big><strong>%s</strong></big></big>' % linkedname
+        try:
+            path = inspect.getabsfile(object)
+            url = urllib.parse.quote(path)
+            filelink = self.filelink(url, path)
+        except TypeError:
+            filelink = '(built-in)'
+        info = []
+        if hasattr(object, '__version__'):
+            version = str(object.__version__)
+            if version[:11] == '$' + 'Revision: ' and version[-1:] == '$':
+                version = version[11:-1].strip()
+            info.append('version %s' % self.escape(version))
+        if hasattr(object, '__date__'):
+            info.append(self.escape(str(object.__date__)))
+        if info:
+            head = head + ' (%s)' % ', '.join(info)
+        docloc = self.getdocloc(object)
+        if docloc is not None:
+            docloc = '<br><a href="%(docloc)s">Module Reference</a>' % locals()
+        else:
+            docloc = ''
+        result = self.heading(
+            head, '#ffffff', '#7799ee',
+            '<a href=".">index</a><br>' + filelink + docloc)
+
+        modules = inspect.getmembers(object, inspect.ismodule)
+
+        classes, cdict = [], {}
+        for key, value in inspect.getmembers(object, inspect.isclass):
+            # if __all__ exists, believe it.  Otherwise use old heuristic.
+            if (all is not None or
+                (inspect.getmodule(value) or object) is object):
+                if visiblename(key, all, object):
+                    classes.append((key, value))
+                    cdict[key] = cdict[value] = '#' + key
+        for key, value in classes:
+            for base in value.__bases__:
+                key, modname = base.__name__, base.__module__
+                module = sys.modules.get(modname)
+                if modname != name and module and hasattr(module, key):
+                    if getattr(module, key) is base:
+                        if not key in cdict:
+                            cdict[key] = cdict[base] = modname + '.html#' + key
+        funcs, fdict = [], {}
+        for key, value in inspect.getmembers(object, inspect.isroutine):
+            # if __all__ exists, believe it.  Otherwise use old heuristic.
+            if (all is not None or
+                inspect.isbuiltin(value) or inspect.getmodule(value) is object):
+                if visiblename(key, all, object):
+                    funcs.append((key, value))
+                    fdict[key] = '#-' + key
+                    if inspect.isfunction(value): fdict[value] = fdict[key]
+        data = []
+        for key, value in inspect.getmembers(object, isdata):
+            if visiblename(key, all, object):
+                data.append((key, value))
+
+        doc = self.markup(getdoc(object), self.preformat, fdict, cdict)
+        doc = doc and '<tt>%s</tt>' % doc
+        result = result + '<p>%s</p>\n' % doc
+
+        if hasattr(object, '__path__'):
+            modpkgs = []
+            for importer, modname, ispkg in pkgutil.iter_modules(object.__path__):
+                modpkgs.append((modname, name, ispkg, 0))
+            modpkgs.sort()
+            contents = self.multicolumn(modpkgs, self.modpkglink)
+            result = result + self.bigsection(
+                'Package Contents', '#ffffff', '#aa55cc', contents)
+        elif modules:
+            contents = self.multicolumn(
+                modules, lambda t: self.modulelink(t[1]))
+            result = result + self.bigsection(
+                'Modules', '#ffffff', '#aa55cc', contents)
+
+        if classes:
+            classlist = [value for (key, value) in classes]
+            contents = [
+                self.formattree(inspect.getclasstree(classlist, 1), name)]
+            for key, value in classes:
+                contents.append(self.document(value, key, name, fdict, cdict))
+            result = result + self.bigsection(
+                'Classes', '#ffffff', '#ee77aa', ' '.join(contents))
+        if funcs:
+            contents = []
+            for key, value in funcs:
+                contents.append(self.document(value, key, name, fdict, cdict))
+            result = result + self.bigsection(
+                'Functions', '#ffffff', '#eeaa77', ' '.join(contents))
+        if data:
+            contents = []
+            for key, value in data:
+                contents.append(self.document(value, key))
+            result = result + self.bigsection(
+                'Data', '#ffffff', '#55aa55', '<br>\n'.join(contents))
+        if hasattr(object, '__author__'):
+            contents = self.markup(str(object.__author__), self.preformat)
+            result = result + self.bigsection(
+                'Author', '#ffffff', '#7799ee', contents)
+        if hasattr(object, '__credits__'):
+            contents = self.markup(str(object.__credits__), self.preformat)
+            result = result + self.bigsection(
+                'Credits', '#ffffff', '#7799ee', contents)
+
+        return result
+
+    def docclass(self, object, name=None, mod=None, funcs={}, classes={},
+                 *ignored):
+        """Produce HTML documentation for a class object."""
+        realname = object.__name__
+        name = name or realname
+        bases = object.__bases__
+
+        contents = []
+        push = contents.append
+
+        # Cute little class to pump out a horizontal rule between sections.
+        class HorizontalRule:
+            def __init__(self):
+                self.needone = 0
+            def maybe(self):
+                if self.needone:
+                    push('<hr>\n')
+                self.needone = 1
+        hr = HorizontalRule()
+
+        # List the mro, if non-trivial.
+        mro = deque(inspect.getmro(object))
+        if len(mro) > 2:
+            hr.maybe()
+            push('<dl><dt>Method resolution order:</dt>\n')
+            for base in mro:
+                push('<dd>%s</dd>\n' % self.classlink(base,
+                                                      object.__module__))
+            push('</dl>\n')
+
+        def spill(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    try:
+                        value = getattr(object, name)
+                    except Exception:
+                        # Some descriptors may meet a failure in their __get__.
+                        # (bug #1785)
+                        push(self.docdata(value, name, mod))
+                    else:
+                        push(self.document(value, name, mod,
+                                        funcs, classes, mdict, object))
+                    push('\n')
+            return attrs
+
+        def spilldescriptors(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    push(self.docdata(value, name, mod))
+            return attrs
+
+        def spilldata(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    base = self.docother(getattr(object, name), name, mod)
+                    doc = getdoc(value)
+                    if not doc:
+                        push('<dl><dt>%s</dl>\n' % base)
+                    else:
+                        doc = self.markup(getdoc(value), self.preformat,
+                                          funcs, classes, mdict)
+                        doc = '<dd><tt>%s</tt>' % doc
+                        push('<dl><dt>%s%s</dl>\n' % (base, doc))
+                    push('\n')
+            return attrs
+
+        attrs = [(name, kind, cls, value)
+                 for name, kind, cls, value in classify_class_attrs(object)
+                 if visiblename(name, obj=object)]
+
+        mdict = {}
+        for key, kind, homecls, value in attrs:
+            mdict[key] = anchor = '#' + name + '-' + key
+            try:
+                value = getattr(object, name)
+            except Exception:
+                # Some descriptors may meet a failure in their __get__.
+                # (bug #1785)
+                pass
+            try:
+                # The value may not be hashable (e.g., a data attr with
+                # a dict or list value).
+                mdict[value] = anchor
+            except TypeError:
+                pass
+
+        while attrs:
+            if mro:
+                thisclass = mro.popleft()
+            else:
+                thisclass = attrs[0][2]
+            attrs, inherited = _split_list(attrs, lambda t: t[2] is thisclass)
+
+            if object is not builtins.object and thisclass is builtins.object:
+                attrs = inherited
+                continue
+            elif thisclass is object:
+                tag = 'defined here'
+            else:
+                tag = 'inherited from %s' % self.classlink(thisclass,
+                                                           object.__module__)
+            tag += ':<br>\n'
+
+            sort_attributes(attrs, object)
+
+            # Pump out the attrs, segregated by kind.
+            attrs = spill('Methods %s' % tag, attrs,
+                          lambda t: t[1] == 'method')
+            attrs = spill('Class methods %s' % tag, attrs,
+                          lambda t: t[1] == 'class method')
+            attrs = spill('Static methods %s' % tag, attrs,
+                          lambda t: t[1] == 'static method')
+            attrs = spilldescriptors("Readonly properties %s" % tag, attrs,
+                                     lambda t: t[1] == 'readonly property')
+            attrs = spilldescriptors('Data descriptors %s' % tag, attrs,
+                                     lambda t: t[1] == 'data descriptor')
+            attrs = spilldata('Data and other attributes %s' % tag, attrs,
+                              lambda t: t[1] == 'data')
+            assert attrs == []
+            attrs = inherited
+
+        contents = ''.join(contents)
+
+        if name == realname:
+            title = '<a name="%s">class <strong>%s</strong></a>' % (
+                name, realname)
+        else:
+            title = '<strong>%s</strong> = <a name="%s">class %s</a>' % (
+                name, name, realname)
+        if bases:
+            parents = []
+            for base in bases:
+                parents.append(self.classlink(base, object.__module__))
+            title = title + '(%s)' % ', '.join(parents)
+
+        decl = ''
+        try:
+            signature = inspect.signature(object)
+        except (ValueError, TypeError):
+            signature = None
+        if signature:
+            argspec = str(signature)
+            if argspec and argspec != '()':
+                decl = name + self.escape(argspec) + '\n\n'
+
+        doc = getdoc(object)
+        if decl:
+            doc = decl + (doc or '')
+        doc = self.markup(doc, self.preformat, funcs, classes, mdict)
+        doc = doc and '<tt>%s<br>&nbsp;</tt>' % doc
+
+        return self.section(title, '#000000', '#ffc8d8', contents, 3, doc)
+
+    def formatvalue(self, object):
+        """Format an argument default value as text."""
+        return self.grey('=' + self.repr(object))
+
+    def docroutine(self, object, name=None, mod=None,
+                   funcs={}, classes={}, methods={}, cl=None):
+        """Produce HTML documentation for a function or method object."""
+        realname = object.__name__
+        name = name or realname
+        anchor = (cl and cl.__name__ or '') + '-' + name
+        note = ''
+        skipdocs = 0
+        if _is_bound_method(object):
+            imclass = object.__self__.__class__
+            if cl:
+                if imclass is not cl:
+                    note = ' from ' + self.classlink(imclass, mod)
+            else:
+                if object.__self__ is not None:
+                    note = ' method of %s instance' % self.classlink(
+                        object.__self__.__class__, mod)
+                else:
+                    note = ' unbound %s method' % self.classlink(imclass,mod)
+
+        if (inspect.iscoroutinefunction(object) or
+                inspect.isasyncgenfunction(object)):
+            asyncqualifier = 'async '
+        else:
+            asyncqualifier = ''
+
+        if name == realname:
+            title = '<a name="%s"><strong>%s</strong></a>' % (anchor, realname)
+        else:
+            if cl and inspect.getattr_static(cl, realname, []) is object:
+                reallink = '<a href="#%s">%s</a>' % (
+                    cl.__name__ + '-' + realname, realname)
+                skipdocs = 1
+            else:
+                reallink = realname
+            title = '<a name="%s"><strong>%s</strong></a> = %s' % (
+                anchor, name, reallink)
+        argspec = None
+        if inspect.isroutine(object):
+            try:
+                signature = inspect.signature(object)
+            except (ValueError, TypeError):
+                signature = None
+            if signature:
+                argspec = str(signature)
+                if realname == '<lambda>':
+                    title = '<strong>%s</strong> <em>lambda</em> ' % name
+                    # XXX lambda's won't usually have func_annotations['return']
+                    # since the syntax doesn't support but it is possible.
+                    # So removing parentheses isn't truly safe.
+                    argspec = argspec[1:-1] # remove parentheses
+        if not argspec:
+            argspec = '(...)'
+
+        decl = asyncqualifier + title + self.escape(argspec) + (note and
+               self.grey('<font face="helvetica, arial">%s</font>' % note))
+
+        if skipdocs:
+            return '<dl><dt>%s</dt></dl>\n' % decl
+        else:
+            doc = self.markup(
+                getdoc(object), self.preformat, funcs, classes, methods)
+            doc = doc and '<dd><tt>%s</tt></dd>' % doc
+            return '<dl><dt>%s</dt>%s</dl>\n' % (decl, doc)
+
+    def docdata(self, object, name=None, mod=None, cl=None):
+        """Produce html documentation for a data descriptor."""
+        results = []
+        push = results.append
+
+        if name:
+            push('<dl><dt><strong>%s</strong></dt>\n' % name)
+        doc = self.markup(getdoc(object), self.preformat)
+        if doc:
+            push('<dd><tt>%s</tt></dd>\n' % doc)
+        push('</dl>\n')
+
+        return ''.join(results)
+
+    docproperty = docdata
+
+    def docother(self, object, name=None, mod=None, *ignored):
+        """Produce HTML documentation for a data object."""
+        lhs = name and '<strong>%s</strong> = ' % name or ''
+        return lhs + self.repr(object)
+
+    def index(self, dir, shadowed=None):
+        """Generate an HTML index for a directory of modules."""
+        modpkgs = []
+        if shadowed is None: shadowed = {}
+        for importer, name, ispkg in pkgutil.iter_modules([dir]):
+            if any((0xD800 <= ord(ch) <= 0xDFFF) for ch in name):
+                # ignore a module if its name contains a surrogate character
+                continue
+            modpkgs.append((name, '', ispkg, name in shadowed))
+            shadowed[name] = 1
+
+        modpkgs.sort()
+        contents = self.multicolumn(modpkgs, self.modpkglink)
+        return self.bigsection(dir, '#ffffff', '#ee77aa', contents)
+
+# -------------------------------------------- text documentation generator
+
+class TextRepr(Repr):
+    """Class for safely making a text representation of a Python object."""
+    def __init__(self):
+        Repr.__init__(self)
+        self.maxlist = self.maxtuple = 20
+        self.maxdict = 10
+        self.maxstring = self.maxother = 100
+
+    def repr1(self, x, level):
+        if hasattr(type(x), '__name__'):
+            methodname = 'repr_' + '_'.join(type(x).__name__.split())
+            if hasattr(self, methodname):
+                return getattr(self, methodname)(x, level)
+        return cram(stripid(repr(x)), self.maxother)
+
+    def repr_string(self, x, level):
+        test = cram(x, self.maxstring)
+        testrepr = repr(test)
+        if '\\' in test and '\\' not in replace(testrepr, r'\\', ''):
+            # Backslashes are only literal in the string and are never
+            # needed to make any special characters, so show a raw string.
+            return 'r' + testrepr[0] + test + testrepr[0]
+        return testrepr
+
+    repr_str = repr_string
+
+    def repr_instance(self, x, level):
+        try:
+            return cram(stripid(repr(x)), self.maxstring)
+        except:
+            return '<%s instance>' % x.__class__.__name__
+
+class TextDoc(Doc):
+    """Formatter class for text documentation."""
+
+    # ------------------------------------------- text formatting utilities
+
+    _repr_instance = TextRepr()
+    repr = _repr_instance.repr
+
+    def bold(self, text):
+        """Format a string in bold by overstriking."""
+        return ''.join(ch + '\b' + ch for ch in text)
+
+    def indent(self, text, prefix='    '):
+        """Indent text by prepending a given prefix to each line."""
+        if not text: return ''
+        lines = [prefix + line for line in text.split('\n')]
+        if lines: lines[-1] = lines[-1].rstrip()
+        return '\n'.join(lines)
+
+    def section(self, title, contents):
+        """Format a section with a given heading."""
+        clean_contents = self.indent(contents).rstrip()
+        return self.bold(title) + '\n' + clean_contents + '\n\n'
+
+    # ---------------------------------------------- type-specific routines
+
+    def formattree(self, tree, modname, parent=None, prefix=''):
+        """Render in text a class tree as returned by inspect.getclasstree()."""
+        result = ''
+        for entry in tree:
+            if type(entry) is type(()):
+                c, bases = entry
+                result = result + prefix + classname(c, modname)
+                if bases and bases != (parent,):
+                    parents = (classname(c, modname) for c in bases)
+                    result = result + '(%s)' % ', '.join(parents)
+                result = result + '\n'
+            elif type(entry) is type([]):
+                result = result + self.formattree(
+                    entry, modname, c, prefix + '    ')
+        return result
+
+    def docmodule(self, object, name=None, mod=None):
+        """Produce text documentation for a given module object."""
+        name = object.__name__ # ignore the passed-in name
+        synop, desc = splitdoc(getdoc(object))
+        result = self.section('NAME', name + (synop and ' - ' + synop))
+        all = getattr(object, '__all__', None)
+        docloc = self.getdocloc(object)
+        if docloc is not None:
+            result = result + self.section('MODULE REFERENCE', docloc + """
+
+The following documentation is automatically generated from the Python
+source files.  It may be incomplete, incorrect or include features that
+are considered implementation detail and may vary between Python
+implementations.  When in doubt, consult the module reference at the
+location listed above.
+""")
+
+        if desc:
+            result = result + self.section('DESCRIPTION', desc)
+
+        classes = []
+        for key, value in inspect.getmembers(object, inspect.isclass):
+            # if __all__ exists, believe it.  Otherwise use old heuristic.
+            if (all is not None
+                or (inspect.getmodule(value) or object) is object):
+                if visiblename(key, all, object):
+                    classes.append((key, value))
+        funcs = []
+        for key, value in inspect.getmembers(object, inspect.isroutine):
+            # if __all__ exists, believe it.  Otherwise use old heuristic.
+            if (all is not None or
+                inspect.isbuiltin(value) or inspect.getmodule(value) is object):
+                if visiblename(key, all, object):
+                    funcs.append((key, value))
+        data = []
+        for key, value in inspect.getmembers(object, isdata):
+            if visiblename(key, all, object):
+                data.append((key, value))
+
+        modpkgs = []
+        modpkgs_names = set()
+        if hasattr(object, '__path__'):
+            for importer, modname, ispkg in pkgutil.iter_modules(object.__path__):
+                modpkgs_names.add(modname)
+                if ispkg:
+                    modpkgs.append(modname + ' (package)')
+                else:
+                    modpkgs.append(modname)
+
+            modpkgs.sort()
+            result = result + self.section(
+                'PACKAGE CONTENTS', '\n'.join(modpkgs))
+
+        # Detect submodules as sometimes created by C extensions
+        submodules = []
+        for key, value in inspect.getmembers(object, inspect.ismodule):
+            if value.__name__.startswith(name + '.') and key not in modpkgs_names:
+                submodules.append(key)
+        if submodules:
+            submodules.sort()
+            result = result + self.section(
+                'SUBMODULES', '\n'.join(submodules))
+
+        if classes:
+            classlist = [value for key, value in classes]
+            contents = [self.formattree(
+                inspect.getclasstree(classlist, 1), name)]
+            for key, value in classes:
+                contents.append(self.document(value, key, name))
+            result = result + self.section('CLASSES', '\n'.join(contents))
+
+        if funcs:
+            contents = []
+            for key, value in funcs:
+                contents.append(self.document(value, key, name))
+            result = result + self.section('FUNCTIONS', '\n'.join(contents))
+
+        if data:
+            contents = []
+            for key, value in data:
+                contents.append(self.docother(value, key, name, maxlen=70))
+            result = result + self.section('DATA', '\n'.join(contents))
+
+        if hasattr(object, '__version__'):
+            version = str(object.__version__)
+            if version[:11] == '$' + 'Revision: ' and version[-1:] == '$':
+                version = version[11:-1].strip()
+            result = result + self.section('VERSION', version)
+        if hasattr(object, '__date__'):
+            result = result + self.section('DATE', str(object.__date__))
+        if hasattr(object, '__author__'):
+            result = result + self.section('AUTHOR', str(object.__author__))
+        if hasattr(object, '__credits__'):
+            result = result + self.section('CREDITS', str(object.__credits__))
+        try:
+            file = inspect.getabsfile(object)
+        except TypeError:
+            file = '(built-in)'
+        result = result + self.section('FILE', file)
+        return result
+
+    def docclass(self, object, name=None, mod=None, *ignored):
+        """Produce text documentation for a given class object."""
+        realname = object.__name__
+        name = name or realname
+        bases = object.__bases__
+
+        def makename(c, m=object.__module__):
+            return classname(c, m)
+
+        if name == realname:
+            title = 'class ' + self.bold(realname)
+        else:
+            title = self.bold(name) + ' = class ' + realname
+        if bases:
+            parents = map(makename, bases)
+            title = title + '(%s)' % ', '.join(parents)
+
+        contents = []
+        push = contents.append
+
+        try:
+            signature = inspect.signature(object)
+        except (ValueError, TypeError):
+            signature = None
+        if signature:
+            argspec = str(signature)
+            if argspec and argspec != '()':
+                push(name + argspec + '\n')
+
+        doc = getdoc(object)
+        if doc:
+            push(doc + '\n')
+
+        # List the mro, if non-trivial.
+        mro = deque(inspect.getmro(object))
+        if len(mro) > 2:
+            push("Method resolution order:")
+            for base in mro:
+                push('    ' + makename(base))
+            push('')
+
+        # List the built-in subclasses, if any:
+        subclasses = sorted(
+            (str(cls.__name__) for cls in type.__subclasses__(object)
+             if not cls.__name__.startswith("_") and cls.__module__ == "builtins"),
+            key=str.lower
+        )
+        no_of_subclasses = len(subclasses)
+        MAX_SUBCLASSES_TO_DISPLAY = 4
+        if subclasses:
+            push("Built-in subclasses:")
+            for subclassname in subclasses[:MAX_SUBCLASSES_TO_DISPLAY]:
+                push('    ' + subclassname)
+            if no_of_subclasses > MAX_SUBCLASSES_TO_DISPLAY:
+                push('    ... and ' +
+                     str(no_of_subclasses - MAX_SUBCLASSES_TO_DISPLAY) +
+                     ' other subclasses')
+            push('')
+
+        # Cute little class to pump out a horizontal rule between sections.
+        class HorizontalRule:
+            def __init__(self):
+                self.needone = 0
+            def maybe(self):
+                if self.needone:
+                    push('-' * 70)
+                self.needone = 1
+        hr = HorizontalRule()
+
+        def spill(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    try:
+                        value = getattr(object, name)
+                    except Exception:
+                        # Some descriptors may meet a failure in their __get__.
+                        # (bug #1785)
+                        push(self.docdata(value, name, mod))
+                    else:
+                        push(self.document(value,
+                                        name, mod, object))
+            return attrs
+
+        def spilldescriptors(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    push(self.docdata(value, name, mod))
+            return attrs
+
+        def spilldata(msg, attrs, predicate):
+            ok, attrs = _split_list(attrs, predicate)
+            if ok:
+                hr.maybe()
+                push(msg)
+                for name, kind, homecls, value in ok:
+                    doc = getdoc(value)
+                    try:
+                        obj = getattr(object, name)
+                    except AttributeError:
+                        obj = homecls.__dict__[name]
+                    push(self.docother(obj, name, mod, maxlen=70, doc=doc) +
+                         '\n')
+            return attrs
+
+        attrs = [(name, kind, cls, value)
+                 for name, kind, cls, value in classify_class_attrs(object)
+                 if visiblename(name, obj=object)]
+
+        while attrs:
+            if mro:
+                thisclass = mro.popleft()
+            else:
+                thisclass = attrs[0][2]
+            attrs, inherited = _split_list(attrs, lambda t: t[2] is thisclass)
+
+            if object is not builtins.object and thisclass is builtins.object:
+                attrs = inherited
+                continue
+            elif thisclass is object:
+                tag = "defined here"
+            else:
+                tag = "inherited from %s" % classname(thisclass,
+                                                      object.__module__)
+
+            sort_attributes(attrs, object)
+
+            # Pump out the attrs, segregated by kind.
+            attrs = spill("Methods %s:\n" % tag, attrs,
+                          lambda t: t[1] == 'method')
+            attrs = spill("Class methods %s:\n" % tag, attrs,
+                          lambda t: t[1] == 'class method')
+            attrs = spill("Static methods %s:\n" % tag, attrs,
+                          lambda t: t[1] == 'static method')
+            attrs = spilldescriptors("Readonly properties %s:\n" % tag, attrs,
+                                     lambda t: t[1] == 'readonly property')
+            attrs = spilldescriptors("Data descriptors %s:\n" % tag, attrs,
+                                     lambda t: t[1] == 'data descriptor')
+            attrs = spilldata("Data and other attributes %s:\n" % tag, attrs,
+                              lambda t: t[1] == 'data')
+
+            assert attrs == []
+            attrs = inherited
+
+        contents = '\n'.join(contents)
+        if not contents:
+            return title + '\n'
+        return title + '\n' + self.indent(contents.rstrip(), ' |  ') + '\n'
+
+    def formatvalue(self, object):
+        """Format an argument default value as text."""
+        return '=' + self.repr(object)
+
+    def docroutine(self, object, name=None, mod=None, cl=None):
+        """Produce text documentation for a function or method object."""
+        realname = object.__name__
+        name = name or realname
+        note = ''
+        skipdocs = 0
+        if _is_bound_method(object):
+            imclass = object.__self__.__class__
+            if cl:
+                if imclass is not cl:
+                    note = ' from ' + classname(imclass, mod)
+            else:
+                if object.__self__ is not None:
+                    note = ' method of %s instance' % classname(
+                        object.__self__.__class__, mod)
+                else:
+                    note = ' unbound %s method' % classname(imclass,mod)
+
+        if (inspect.iscoroutinefunction(object) or
+                inspect.isasyncgenfunction(object)):
+            asyncqualifier = 'async '
+        else:
+            asyncqualifier = ''
+
+        if name == realname:
+            title = self.bold(realname)
+        else:
+            if cl and inspect.getattr_static(cl, realname, []) is object:
+                skipdocs = 1
+            title = self.bold(name) + ' = ' + realname
+        argspec = None
+
+        if inspect.isroutine(object):
+            try:
+                signature = inspect.signature(object)
+            except (ValueError, TypeError):
+                signature = None
+            if signature:
+                argspec = str(signature)
+                if realname == '<lambda>':
+                    title = self.bold(name) + ' lambda '
+                    # XXX lambda's won't usually have func_annotations['return']
+                    # since the syntax doesn't support but it is possible.
+                    # So removing parentheses isn't truly safe.
+                    argspec = argspec[1:-1] # remove parentheses
+        if not argspec:
+            argspec = '(...)'
+        decl = asyncqualifier + title + argspec + note
+
+        if skipdocs:
+            return decl + '\n'
+        else:
+            doc = getdoc(object) or ''
+            return decl + '\n' + (doc and self.indent(doc).rstrip() + '\n')
+
+    def docdata(self, object, name=None, mod=None, cl=None):
+        """Produce text documentation for a data descriptor."""
+        results = []
+        push = results.append
+
+        if name:
+            push(self.bold(name))
+            push('\n')
+        doc = getdoc(object) or ''
+        if doc:
+            push(self.indent(doc))
+            push('\n')
+        return ''.join(results)
+
+    docproperty = docdata
+
+    def docother(self, object, name=None, mod=None, parent=None, maxlen=None, doc=None):
+        """Produce text documentation for a data object."""
+        repr = self.repr(object)
+        if maxlen:
+            line = (name and name + ' = ' or '') + repr
+            chop = maxlen - len(line)
+            if chop < 0: repr = repr[:chop] + '...'
+        line = (name and self.bold(name) + ' = ' or '') + repr
+        if not doc:
+            doc = getdoc(object)
+        if doc:
+            line += '\n' + self.indent(str(doc)) + '\n'
+        return line
+
+class _PlainTextDoc(TextDoc):
+    """Subclass of TextDoc which overrides string styling"""
+    def bold(self, text):
+        return text
+
+# --------------------------------------------------------- user interfaces
+
+def pager(text):
+    """The first time this is called, determine what kind of pager to use."""
+    global pager
+    pager = getpager()
+    pager(text)
+
+def getpager():
+    """Decide what method to use for paging through text."""
+    if not hasattr(sys.stdin, "isatty"):
+        return plainpager
+    if not hasattr(sys.stdout, "isatty"):
+        return plainpager
+    if not sys.stdin.isatty() or not sys.stdout.isatty():
+        return plainpager
+    use_pager = os.environ.get('MANPAGER') or os.environ.get('PAGER')
+    if use_pager:
+        if sys.platform == 'win32': # pipes completely broken in Windows
+            return lambda text: tempfilepager(plain(text), use_pager)
+        elif os.environ.get('TERM') in ('dumb', 'emacs'):
+            return lambda text: pipepager(plain(text), use_pager)
+        else:
+            return lambda text: pipepager(text, use_pager)
+    if os.environ.get('TERM') in ('dumb', 'emacs'):
+        return plainpager
+    if sys.platform == 'win32':
+        return lambda text: tempfilepager(plain(text), 'more <')
+    if hasattr(os, 'system') and os.system('(less) 2>/dev/null') == 0:
+        return lambda text: pipepager(text, 'less')
+
+    import tempfile
+    (fd, filename) = tempfile.mkstemp()
+    os.close(fd)
+    try:
+        if hasattr(os, 'system') and os.system('more "%s"' % filename) == 0:
+            return lambda text: pipepager(text, 'more')
+        else:
+            return ttypager
+    finally:
+        os.unlink(filename)
+
+def plain(text):
+    """Remove boldface formatting from text."""
+    return re.sub('.\b', '', text)
+
+def pipepager(text, cmd):
+    """Page through text by feeding it to another program."""
+    import subprocess
+    proc = subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE)
+    try:
+        with io.TextIOWrapper(proc.stdin, errors='backslashreplace') as pipe:
+            try:
+                pipe.write(text)
+            except KeyboardInterrupt:
+                # We've hereby abandoned whatever text hasn't been written,
+                # but the pager is still in control of the terminal.
+                pass
+    except OSError:
+        pass # Ignore broken pipes caused by quitting the pager program.
+    while True:
+        try:
+            proc.wait()
+            break
+        except KeyboardInterrupt:
+            # Ignore ctl-c like the pager itself does.  Otherwise the pager is
+            # left running and the terminal is in raw mode and unusable.
+            pass
+
+def tempfilepager(text, cmd):
+    """Page through text by invoking a program on a temporary file."""
+    import tempfile
+    with tempfile.TemporaryDirectory() as tempdir:
+        filename = os.path.join(tempdir, 'pydoc.out')
+        with open(filename, 'w', errors='backslashreplace',
+                  encoding=os.device_encoding(0) if
+                  sys.platform == 'win32' else None
+                  ) as file:
+            file.write(text)
+        os.system(cmd + ' "' + filename + '"')
+
+def _escape_stdout(text):
+    # Escape non-encodable characters to avoid encoding errors later
+    encoding = getattr(sys.stdout, 'encoding', None) or 'utf-8'
+    return text.encode(encoding, 'backslashreplace').decode(encoding)
+
+def ttypager(text):
+    """Page through text on a text terminal."""
+    lines = plain(_escape_stdout(text)).split('\n')
+    try:
+        import tty
+        fd = sys.stdin.fileno()
+        old = tty.tcgetattr(fd)
+        tty.setcbreak(fd)
+        getchar = lambda: sys.stdin.read(1)
+    except (ImportError, AttributeError, io.UnsupportedOperation):
+        tty = None
+        getchar = lambda: sys.stdin.readline()[:-1][:1]
+
+    try:
+        try:
+            h = int(os.environ.get('LINES', 0))
+        except ValueError:
+            h = 0
+        if h <= 1:
+            h = 25
+        r = inc = h - 1
+        sys.stdout.write('\n'.join(lines[:inc]) + '\n')
+        while lines[r:]:
+            sys.stdout.write('-- more --')
+            sys.stdout.flush()
+            c = getchar()
+
+            if c in ('q', 'Q'):
+                sys.stdout.write('\r          \r')
+                break
+            elif c in ('\r', '\n'):
+                sys.stdout.write('\r          \r' + lines[r] + '\n')
+                r = r + 1
+                continue
+            if c in ('b', 'B', '\x1b'):
+                r = r - inc - inc
+                if r < 0: r = 0
+            sys.stdout.write('\n' + '\n'.join(lines[r:r+inc]) + '\n')
+            r = r + inc
+
+    finally:
+        if tty:
+            tty.tcsetattr(fd, tty.TCSAFLUSH, old)
+
+def plainpager(text):
+    """Simply print unformatted text.  This is the ultimate fallback."""
+    sys.stdout.write(plain(_escape_stdout(text)))
+
+def describe(thing):
+    """Produce a short description of the given thing."""
+    if inspect.ismodule(thing):
+        if thing.__name__ in sys.builtin_module_names:
+            return 'built-in module ' + thing.__name__
+        if hasattr(thing, '__path__'):
+            return 'package ' + thing.__name__
+        else:
+            return 'module ' + thing.__name__
+    if inspect.isbuiltin(thing):
+        return 'built-in function ' + thing.__name__
+    if inspect.isgetsetdescriptor(thing):
+        return 'getset descriptor %s.%s.%s' % (
+            thing.__objclass__.__module__, thing.__objclass__.__name__,
+            thing.__name__)
+    if inspect.ismemberdescriptor(thing):
+        return 'member descriptor %s.%s.%s' % (
+            thing.__objclass__.__module__, thing.__objclass__.__name__,
+            thing.__name__)
+    if inspect.isclass(thing):
+        return 'class ' + thing.__name__
+    if inspect.isfunction(thing):
+        return 'function ' + thing.__name__
+    if inspect.ismethod(thing):
+        return 'method ' + thing.__name__
+    return type(thing).__name__
+
+def locate(path, forceload=0):
+    """Locate an object by name or dotted path, importing as necessary."""
+    parts = [part for part in path.split('.') if part]
+    module, n = None, 0
+    while n < len(parts):
+        nextmodule = safeimport('.'.join(parts[:n+1]), forceload)
+        if nextmodule: module, n = nextmodule, n + 1
+        else: break
+    if module:
+        object = module
+    else:
+        object = builtins
+    for part in parts[n:]:
+        try:
+            object = getattr(object, part)
+        except AttributeError:
+            return None
+    return object
+
+# --------------------------------------- interactive interpreter interface
+
+text = TextDoc()
+plaintext = _PlainTextDoc()
+html = HTMLDoc()
+
+def resolve(thing, forceload=0):
+    """Given an object or a path to an object, get the object and its name."""
+    if isinstance(thing, str):
+        object = locate(thing, forceload)
+        if object is None:
+            raise ImportError('''\
+No Python documentation found for %r.
+Use help() to get the interactive help utility.
+Use help(str) for help on the str class.''' % thing)
+        return object, thing
+    else:
+        name = getattr(thing, '__name__', None)
+        return thing, name if isinstance(name, str) else None
+
+def render_doc(thing, title='Python Library Documentation: %s', forceload=0,
+        renderer=None):
+    """Render text documentation, given an object or a path to an object."""
+    if renderer is None:
+        renderer = text
+    object, name = resolve(thing, forceload)
+    desc = describe(object)
+    module = inspect.getmodule(object)
+    if name and '.' in name:
+        desc += ' in ' + name[:name.rfind('.')]
+    elif module and module is not object:
+        desc += ' in module ' + module.__name__
+
+    if not (inspect.ismodule(object) or
+              inspect.isclass(object) or
+              inspect.isroutine(object) or
+              inspect.isdatadescriptor(object) or
+              _getdoc(object)):
+        # If the passed object is a piece of data or an instance,
+        # document its available methods instead of its value.
+        if hasattr(object, '__origin__'):
+            object = object.__origin__
+        else:
+            object = type(object)
+            desc += ' object'
+    return title % desc + '\n\n' + renderer.document(object, name)
+
+def doc(thing, title='Python Library Documentation: %s', forceload=0,
+        output=None):
+    """Display text documentation, given an object or a path to an object."""
+    try:
+        if output is None:
+            pager(render_doc(thing, title, forceload))
+        else:
+            output.write(render_doc(thing, title, forceload, plaintext))
+    except (ImportError, ErrorDuringImport) as value:
+        print(value)
+
+def writedoc(thing, forceload=0):
+    """Write HTML documentation to a file in the current directory."""
+    try:
+        object, name = resolve(thing, forceload)
+        page = html.page(describe(object), html.document(object, name))
+        with open(name + '.html', 'w', encoding='utf-8') as file:
+            file.write(page)
+        print('wrote', name + '.html')
+    except (ImportError, ErrorDuringImport) as value:
+        print(value)
+
+def writedocs(dir, pkgpath='', done=None):
+    """Write out HTML documentation for all modules in a directory tree."""
+    if done is None: done = {}
+    for importer, modname, ispkg in pkgutil.walk_packages([dir], pkgpath):
+        writedoc(modname)
+    return
+
+class Helper:
+
+    # These dictionaries map a topic name to either an alias, or a tuple
+    # (label, seealso-items).  The "label" is the label of the corresponding
+    # section in the .rst file under Doc/ and an index into the dictionary
+    # in pydoc_data/topics.py.
+    #
+    # CAUTION: if you change one of these dictionaries, be sure to adapt the
+    #          list of needed labels in Doc/tools/extensions/pyspecific.py and
+    #          regenerate the pydoc_data/topics.py file by running
+    #              make pydoc-topics
+    #          in Doc/ and copying the output file into the Lib/ directory.
+
+    keywords = {
+        'False': '',
+        'None': '',
+        'True': '',
+        '__peg_parser__': '',
+        'and': 'BOOLEAN',
+        'as': 'with',
+        'assert': ('assert', ''),
+        'async': ('async', ''),
+        'await': ('await', ''),
+        'break': ('break', 'while for'),
+        'class': ('class', 'CLASSES SPECIALMETHODS'),
+        'continue': ('continue', 'while for'),
+        'def': ('function', ''),
+        'del': ('del', 'BASICMETHODS'),
+        'elif': 'if',
+        'else': ('else', 'while for'),
+        'except': 'try',
+        'finally': 'try',
+        'for': ('for', 'break continue while'),
+        'from': 'import',
+        'global': ('global', 'nonlocal NAMESPACES'),
+        'if': ('if', 'TRUTHVALUE'),
+        'import': ('import', 'MODULES'),
+        'in': ('in', 'SEQUENCEMETHODS'),
+        'is': 'COMPARISON',
+        'lambda': ('lambda', 'FUNCTIONS'),
+        'nonlocal': ('nonlocal', 'global NAMESPACES'),
+        'not': 'BOOLEAN',
+        'or': 'BOOLEAN',
+        'pass': ('pass', ''),
+        'raise': ('raise', 'EXCEPTIONS'),
+        'return': ('return', 'FUNCTIONS'),
+        'try': ('try', 'EXCEPTIONS'),
+        'while': ('while', 'break continue if TRUTHVALUE'),
+        'with': ('with', 'CONTEXTMANAGERS EXCEPTIONS yield'),
+        'yield': ('yield', ''),
+    }
+    # Either add symbols to this dictionary or to the symbols dictionary
+    # directly: Whichever is easier. They are merged later.
+    _strprefixes = [p + q for p in ('b', 'f', 'r', 'u') for q in ("'", '"')]
+    _symbols_inverse = {
+        'STRINGS' : ("'", "'''", '"', '"""', *_strprefixes),
+        'OPERATORS' : ('+', '-', '*', '**', '/', '//', '%', '<<', '>>', '&',
+                       '|', '^', '~', '<', '>', '<=', '>=', '==', '!=', '<>'),
+        'COMPARISON' : ('<', '>', '<=', '>=', '==', '!=', '<>'),
+        'UNARY' : ('-', '~'),
+        'AUGMENTEDASSIGNMENT' : ('+=', '-=', '*=', '/=', '%=', '&=', '|=',
+                                '^=', '<<=', '>>=', '**=', '//='),
+        'BITWISE' : ('<<', '>>', '&', '|', '^', '~'),
+        'COMPLEX' : ('j', 'J')
+    }
+    symbols = {
+        '%': 'OPERATORS FORMATTING',
+        '**': 'POWER',
+        ',': 'TUPLES LISTS FUNCTIONS',
+        '.': 'ATTRIBUTES FLOAT MODULES OBJECTS',
+        '...': 'ELLIPSIS',
+        ':': 'SLICINGS DICTIONARYLITERALS',
+        '@': 'def class',
+        '\\': 'STRINGS',
+        '_': 'PRIVATENAMES',
+        '__': 'PRIVATENAMES SPECIALMETHODS',
+        '`': 'BACKQUOTES',
+        '(': 'TUPLES FUNCTIONS CALLS',
+        ')': 'TUPLES FUNCTIONS CALLS',
+        '[': 'LISTS SUBSCRIPTS SLICINGS',
+        ']': 'LISTS SUBSCRIPTS SLICINGS'
+    }
+    for topic, symbols_ in _symbols_inverse.items():
+        for symbol in symbols_:
+            topics = symbols.get(symbol, topic)
+            if topic not in topics:
+                topics = topics + ' ' + topic
+            symbols[symbol] = topics
+
+    topics = {
+        'TYPES': ('types', 'STRINGS UNICODE NUMBERS SEQUENCES MAPPINGS '
+                  'FUNCTIONS CLASSES MODULES FILES inspect'),
+        'STRINGS': ('strings', 'str UNICODE SEQUENCES STRINGMETHODS '
+                    'FORMATTING TYPES'),
+        'STRINGMETHODS': ('string-methods', 'STRINGS FORMATTING'),
+        'FORMATTING': ('formatstrings', 'OPERATORS'),
+        'UNICODE': ('strings', 'encodings unicode SEQUENCES STRINGMETHODS '
+                    'FORMATTING TYPES'),
+        'NUMBERS': ('numbers', 'INTEGER FLOAT COMPLEX TYPES'),
+        'INTEGER': ('integers', 'int range'),
+        'FLOAT': ('floating', 'float math'),
+        'COMPLEX': ('imaginary', 'complex cmath'),
+        'SEQUENCES': ('typesseq', 'STRINGMETHODS FORMATTING range LISTS'),
+        'MAPPINGS': 'DICTIONARIES',
+        'FUNCTIONS': ('typesfunctions', 'def TYPES'),
+        'METHODS': ('typesmethods', 'class def CLASSES TYPES'),
+        'CODEOBJECTS': ('bltin-code-objects', 'compile FUNCTIONS TYPES'),
+        'TYPEOBJECTS': ('bltin-type-objects', 'types TYPES'),
+        'FRAMEOBJECTS': 'TYPES',
+        'TRACEBACKS': 'TYPES',
+        'NONE': ('bltin-null-object', ''),
+        'ELLIPSIS': ('bltin-ellipsis-object', 'SLICINGS'),
+        'SPECIALATTRIBUTES': ('specialattrs', ''),
+        'CLASSES': ('types', 'class SPECIALMETHODS PRIVATENAMES'),
+        'MODULES': ('typesmodules', 'import'),
+        'PACKAGES': 'import',
+        'EXPRESSIONS': ('operator-summary', 'lambda or and not in is BOOLEAN '
+                        'COMPARISON BITWISE SHIFTING BINARY FORMATTING POWER '
+                        'UNARY ATTRIBUTES SUBSCRIPTS SLICINGS CALLS TUPLES '
+                        'LISTS DICTIONARIES'),
+        'OPERATORS': 'EXPRESSIONS',
+        'PRECEDENCE': 'EXPRESSIONS',
+        'OBJECTS': ('objects', 'TYPES'),
+        'SPECIALMETHODS': ('specialnames', 'BASICMETHODS ATTRIBUTEMETHODS '
+                           'CALLABLEMETHODS SEQUENCEMETHODS MAPPINGMETHODS '
+                           'NUMBERMETHODS CLASSES'),
+        'BASICMETHODS': ('customization', 'hash repr str SPECIALMETHODS'),
+        'ATTRIBUTEMETHODS': ('attribute-access', 'ATTRIBUTES SPECIALMETHODS'),
+        'CALLABLEMETHODS': ('callable-types', 'CALLS SPECIALMETHODS'),
+        'SEQUENCEMETHODS': ('sequence-types', 'SEQUENCES SEQUENCEMETHODS '
+                             'SPECIALMETHODS'),
+        'MAPPINGMETHODS': ('sequence-types', 'MAPPINGS SPECIALMETHODS'),
+        'NUMBERMETHODS': ('numeric-types', 'NUMBERS AUGMENTEDASSIGNMENT '
+                          'SPECIALMETHODS'),
+        'EXECUTION': ('execmodel', 'NAMESPACES DYNAMICFEATURES EXCEPTIONS'),
+        'NAMESPACES': ('naming', 'global nonlocal ASSIGNMENT DELETION DYNAMICFEATURES'),
+        'DYNAMICFEATURES': ('dynamic-features', ''),
+        'SCOPING': 'NAMESPACES',
+        'FRAMES': 'NAMESPACES',
+        'EXCEPTIONS': ('exceptions', 'try except finally raise'),
+        'CONVERSIONS': ('conversions', ''),
+        'IDENTIFIERS': ('identifiers', 'keywords SPECIALIDENTIFIERS'),
+        'SPECIALIDENTIFIERS': ('id-classes', ''),
+        'PRIVATENAMES': ('atom-identifiers', ''),
+        'LITERALS': ('atom-literals', 'STRINGS NUMBERS TUPLELITERALS '
+                     'LISTLITERALS DICTIONARYLITERALS'),
+        'TUPLES': 'SEQUENCES',
+        'TUPLELITERALS': ('exprlists', 'TUPLES LITERALS'),
+        'LISTS': ('typesseq-mutable', 'LISTLITERALS'),
+        'LISTLITERALS': ('lists', 'LISTS LITERALS'),
+        'DICTIONARIES': ('typesmapping', 'DICTIONARYLITERALS'),
+        'DICTIONARYLITERALS': ('dict', 'DICTIONARIES LITERALS'),
+        'ATTRIBUTES': ('attribute-references', 'getattr hasattr setattr ATTRIBUTEMETHODS'),
+        'SUBSCRIPTS': ('subscriptions', 'SEQUENCEMETHODS'),
+        'SLICINGS': ('slicings', 'SEQUENCEMETHODS'),
+        'CALLS': ('calls', 'EXPRESSIONS'),
+        'POWER': ('power', 'EXPRESSIONS'),
+        'UNARY': ('unary', 'EXPRESSIONS'),
+        'BINARY': ('binary', 'EXPRESSIONS'),
+        'SHIFTING': ('shifting', 'EXPRESSIONS'),
+        'BITWISE': ('bitwise', 'EXPRESSIONS'),
+        'COMPARISON': ('comparisons', 'EXPRESSIONS BASICMETHODS'),
+        'BOOLEAN': ('booleans', 'EXPRESSIONS TRUTHVALUE'),
+        'ASSERTION': 'assert',
+        'ASSIGNMENT': ('assignment', 'AUGMENTEDASSIGNMENT'),
+        'AUGMENTEDASSIGNMENT': ('augassign', 'NUMBERMETHODS'),
+        'DELETION': 'del',
+        'RETURNING': 'return',
+        'IMPORTING': 'import',
+        'CONDITIONAL': 'if',
+        'LOOPING': ('compound', 'for while break continue'),
+        'TRUTHVALUE': ('truth', 'if while and or not BASICMETHODS'),
+        'DEBUGGING': ('debugger', 'pdb'),
+        'CONTEXTMANAGERS': ('context-managers', 'with'),
+    }
+
+    def __init__(self, input=None, output=None):
+        self._input = input
+        self._output = output
+
+    @property
+    def input(self):
+        return self._input or sys.stdin
+
+    @property
+    def output(self):
+        return self._output or sys.stdout
+
+    def __repr__(self):
+        if inspect.stack()[1][3] == '?':
+            self()
+            return ''
+        return '<%s.%s instance>' % (self.__class__.__module__,
+                                     self.__class__.__qualname__)
+
+    _GoInteractive = object()
+    def __call__(self, request=_GoInteractive):
+        if request is not self._GoInteractive:
+            self.help(request)
+        else:
+            self.intro()
+            self.interact()
+            self.output.write('''
+You are now leaving help and returning to the Python interpreter.
+If you want to ask for help on a particular object directly from the
+interpreter, you can type "help(object)".  Executing "help('string')"
+has the same effect as typing a particular string at the help> prompt.
+''')
+
+    def interact(self):
+        self.output.write('\n')
+        while True:
+            try:
+                request = self.getline('help> ')
+                if not request: break
+            except (KeyboardInterrupt, EOFError):
+                break
+            request = request.strip()
+
+            # Make sure significant trailing quoting marks of literals don't
+            # get deleted while cleaning input
+            if (len(request) > 2 and request[0] == request[-1] in ("'", '"')
+                    and request[0] not in request[1:-1]):
+                request = request[1:-1]
+            if request.lower() in ('q', 'quit'): break
+            if request == 'help':
+                self.intro()
+            else:
+                self.help(request)
+
+    def getline(self, prompt):
+        """Read one line, using input() when appropriate."""
+        if self.input is sys.stdin:
+            return input(prompt)
+        else:
+            self.output.write(prompt)
+            self.output.flush()
+            return self.input.readline()
+
+    def help(self, request):
+        if type(request) is type(''):
+            request = request.strip()
+            if request == 'keywords': self.listkeywords()
+            elif request == 'symbols': self.listsymbols()
+            elif request == 'topics': self.listtopics()
+            elif request == 'modules': self.listmodules()
+            elif request[:8] == 'modules ':
+                self.listmodules(request.split()[1])
+            elif request in self.symbols: self.showsymbol(request)
+            elif request in ['True', 'False', 'None']:
+                # special case these keywords since they are objects too
+                doc(eval(request), 'Help on %s:')
+            elif request in self.keywords: self.showtopic(request)
+            elif request in self.topics: self.showtopic(request)
+            elif request: doc(request, 'Help on %s:', output=self._output)
+            else: doc(str, 'Help on %s:', output=self._output)
+        elif isinstance(request, Helper): self()
+        else: doc(request, 'Help on %s:', output=self._output)
+        self.output.write('\n')
+
+    def intro(self):
+        self.output.write('''
+Welcome to Python {0}'s help utility!
+
+If this is your first time using Python, you should definitely check out
+the tutorial on the Internet at https://docs.python.org/{0}/tutorial/.
+
+Enter the name of any module, keyword, or topic to get help on writing
+Python programs and using Python modules.  To quit this help utility and
+return to the interpreter, just type "quit".
+
+To get a list of available modules, keywords, symbols, or topics, type
+"modules", "keywords", "symbols", or "topics".  Each module also comes
+with a one-line summary of what it does; to list the modules whose name
+or summary contain a given string such as "spam", type "modules spam".
+'''.format('%d.%d' % sys.version_info[:2]))
+
+    def list(self, items, columns=4, width=80):
+        items = list(sorted(items))
+        colw = width // columns
+        rows = (len(items) + columns - 1) // columns
+        for row in range(rows):
+            for col in range(columns):
+                i = col * rows + row
+                if i < len(items):
+                    self.output.write(items[i])
+                    if col < columns - 1:
+                        self.output.write(' ' + ' ' * (colw - 1 - len(items[i])))
+            self.output.write('\n')
+
+    def listkeywords(self):
+        self.output.write('''
+Here is a list of the Python keywords.  Enter any keyword to get more help.
+
+''')
+        self.list(self.keywords.keys())
+
+    def listsymbols(self):
+        self.output.write('''
+Here is a list of the punctuation symbols which Python assigns special meaning
+to. Enter any symbol to get more help.
+
+''')
+        self.list(self.symbols.keys())
+
+    def listtopics(self):
+        self.output.write('''
+Here is a list of available topics.  Enter any topic name to get more help.
+
+''')
+        self.list(self.topics.keys())
+
+    def showtopic(self, topic, more_xrefs=''):
+        try:
+            import pydoc_data.topics
+        except ImportError:
+            self.output.write('''
+Sorry, topic and keyword documentation is not available because the
+module "pydoc_data.topics" could not be found.
+''')
+            return
+        target = self.topics.get(topic, self.keywords.get(topic))
+        if not target:
+            self.output.write('no documentation found for %s\n' % repr(topic))
+            return
+        if type(target) is type(''):
+            return self.showtopic(target, more_xrefs)
+
+        label, xrefs = target
+        try:
+            doc = pydoc_data.topics.topics[label]
+        except KeyError:
+            self.output.write('no documentation found for %s\n' % repr(topic))
+            return
+        doc = doc.strip() + '\n'
+        if more_xrefs:
+            xrefs = (xrefs or '') + ' ' + more_xrefs
+        if xrefs:
+            import textwrap
+            text = 'Related help topics: ' + ', '.join(xrefs.split()) + '\n'
+            wrapped_text = textwrap.wrap(text, 72)
+            doc += '\n%s\n' % '\n'.join(wrapped_text)
+        pager(doc)
+
+    def _gettopic(self, topic, more_xrefs=''):
+        """Return unbuffered tuple of (topic, xrefs).
+
+        If an error occurs here, the exception is caught and displayed by
+        the url handler.
+
+        This function duplicates the showtopic method but returns its
+        result directly so it can be formatted for display in an html page.
+        """
+        try:
+            import pydoc_data.topics
+        except ImportError:
+            return('''
+Sorry, topic and keyword documentation is not available because the
+module "pydoc_data.topics" could not be found.
+''' , '')
+        target = self.topics.get(topic, self.keywords.get(topic))
+        if not target:
+            raise ValueError('could not find topic')
+        if isinstance(target, str):
+            return self._gettopic(target, more_xrefs)
+        label, xrefs = target
+        doc = pydoc_data.topics.topics[label]
+        if more_xrefs:
+            xrefs = (xrefs or '') + ' ' + more_xrefs
+        return doc, xrefs
+
+    def showsymbol(self, symbol):
+        target = self.symbols[symbol]
+        topic, _, xrefs = target.partition(' ')
+        self.showtopic(topic, xrefs)
+
+    def listmodules(self, key=''):
+        if key:
+            self.output.write('''
+Here is a list of modules whose name or summary contains '{}'.
+If there are any, enter a module name to get more help.
+
+'''.format(key))
+            apropos(key)
+        else:
+            self.output.write('''
+Please wait a moment while I gather a list of all available modules...
+
+''')
+            modules = {}
+            def callback(path, modname, desc, modules=modules):
+                if modname and modname[-9:] == '.__init__':
+                    modname = modname[:-9] + ' (package)'
+                if modname.find('.') < 0:
+                    modules[modname] = 1
+            def onerror(modname):
+                callback(None, modname, None)
+            ModuleScanner().run(callback, onerror=onerror)
+            self.list(modules.keys())
+            self.output.write('''
+Enter any module name to get more help.  Or, type "modules spam" to search
+for modules whose name or summary contain the string "spam".
+''')
+
+help = Helper()
+
+class ModuleScanner:
+    """An interruptible scanner that searches module synopses."""
+
+    def run(self, callback, key=None, completer=None, onerror=None):
+        if key: key = key.lower()
+        self.quit = False
+        seen = {}
+
+        for modname in sys.builtin_module_names:
+            if modname != '__main__':
+                seen[modname] = 1
+                if key is None:
+                    callback(None, modname, '')
+                else:
+                    name = __import__(modname).__doc__ or ''
+                    desc = name.split('\n')[0]
+                    name = modname + ' - ' + desc
+                    if name.lower().find(key) >= 0:
+                        callback(None, modname, desc)
+
+        for importer, modname, ispkg in pkgutil.walk_packages(onerror=onerror):
+            if self.quit:
+                break
+
+            if key is None:
+                callback(None, modname, '')
+            else:
+                try:
+                    spec = pkgutil._get_spec(importer, modname)
+                except SyntaxError:
+                    # raised by tests for bad coding cookies or BOM
+                    continue
+                loader = spec.loader
+                if hasattr(loader, 'get_source'):
+                    try:
+                        source = loader.get_source(modname)
+                    except Exception:
+                        if onerror:
+                            onerror(modname)
+                        continue
+                    desc = source_synopsis(io.StringIO(source)) or ''
+                    if hasattr(loader, 'get_filename'):
+                        path = loader.get_filename(modname)
+                    else:
+                        path = None
+                else:
+                    try:
+                        module = importlib._bootstrap._load(spec)
+                    except ImportError:
+                        if onerror:
+                            onerror(modname)
+                        continue
+                    desc = module.__doc__.splitlines()[0] if module.__doc__ else ''
+                    path = getattr(module,'__file__',None)
+                name = modname + ' - ' + desc
+                if name.lower().find(key) >= 0:
+                    callback(path, modname, desc)
+
+        if completer:
+            completer()
+
+def apropos(key):
+    """Print all the one-line module summaries that contain a substring."""
+    def callback(path, modname, desc):
+        if modname[-9:] == '.__init__':
+            modname = modname[:-9] + ' (package)'
+        print(modname, desc and '- ' + desc)
+    def onerror(modname):
+        pass
+    with warnings.catch_warnings():
+        warnings.filterwarnings('ignore') # ignore problems during import
+        ModuleScanner().run(callback, key, onerror=onerror)
+
+# --------------------------------------- enhanced Web browser interface
+
+def _start_server(urlhandler, hostname, port):
+    """Start an HTTP server thread on a specific port.
+
+    Start an HTML/text server thread, so HTML or text documents can be
+    browsed dynamically and interactively with a Web browser.  Example use:
+
+        >>> import time
+        >>> import pydoc
+
+        Define a URL handler.  To determine what the client is asking
+        for, check the URL and content_type.
+
+        Then get or generate some text or HTML code and return it.
+
+        >>> def my_url_handler(url, content_type):
+        ...     text = 'the URL sent was: (%s, %s)' % (url, content_type)
+        ...     return text
+
+        Start server thread on port 0.
+        If you use port 0, the server will pick a random port number.
+        You can then use serverthread.port to get the port number.
+
+        >>> port = 0
+        >>> serverthread = pydoc._start_server(my_url_handler, port)
+
+        Check that the server is really started.  If it is, open browser
+        and get first page.  Use serverthread.url as the starting page.
+
+        >>> if serverthread.serving:
+        ...    import webbrowser
+
+        The next two lines are commented out so a browser doesn't open if
+        doctest is run on this module.
+
+        #...    webbrowser.open(serverthread.url)
+        #True
+
+        Let the server do its thing. We just need to monitor its status.
+        Use time.sleep so the loop doesn't hog the CPU.
+
+        >>> starttime = time.monotonic()
+        >>> timeout = 1                    #seconds
+
+        This is a short timeout for testing purposes.
+
+        >>> while serverthread.serving:
+        ...     time.sleep(.01)
+        ...     if serverthread.serving and time.monotonic() - starttime > timeout:
+        ...          serverthread.stop()
+        ...          break
+
+        Print any errors that may have occurred.
+
+        >>> print(serverthread.error)
+        None
+   """
+    import http.server
+    import email.message
+    import select
+    import threading
+
+    class DocHandler(http.server.BaseHTTPRequestHandler):
+
+        def do_GET(self):
+            """Process a request from an HTML browser.
+
+            The URL received is in self.path.
+            Get an HTML page from self.urlhandler and send it.
+            """
+            if self.path.endswith('.css'):
+                content_type = 'text/css'
+            else:
+                content_type = 'text/html'
+            self.send_response(200)
+            self.send_header('Content-Type', '%s; charset=UTF-8' % content_type)
+            self.end_headers()
+            self.wfile.write(self.urlhandler(
+                self.path, content_type).encode('utf-8'))
+
+        def log_message(self, *args):
+            # Don't log messages.
+            pass
+
+    class DocServer(http.server.HTTPServer):
+
+        def __init__(self, host, port, callback):
+            self.host = host
+            self.address = (self.host, port)
+            self.callback = callback
+            self.base.__init__(self, self.address, self.handler)
+            self.quit = False
+
+        def serve_until_quit(self):
+            while not self.quit:
+                rd, wr, ex = select.select([self.socket.fileno()], [], [], 1)
+                if rd:
+                    self.handle_request()
+            self.server_close()
+
+        def server_activate(self):
+            self.base.server_activate(self)
+            if self.callback:
+                self.callback(self)
+
+    class ServerThread(threading.Thread):
+
+        def __init__(self, urlhandler, host, port):
+            self.urlhandler = urlhandler
+            self.host = host
+            self.port = int(port)
+            threading.Thread.__init__(self)
+            self.serving = False
+            self.error = None
+
+        def run(self):
+            """Start the server."""
+            try:
+                DocServer.base = http.server.HTTPServer
+                DocServer.handler = DocHandler
+                DocHandler.MessageClass = email.message.Message
+                DocHandler.urlhandler = staticmethod(self.urlhandler)
+                docsvr = DocServer(self.host, self.port, self.ready)
+                self.docserver = docsvr
+                docsvr.serve_until_quit()
+            except Exception as e:
+                self.error = e
+
+        def ready(self, server):
+            self.serving = True
+            self.host = server.host
+            self.port = server.server_port
+            self.url = 'http://%s:%d/' % (self.host, self.port)
+
+        def stop(self):
+            """Stop the server and this thread nicely"""
+            self.docserver.quit = True
+            self.join()
+            # explicitly break a reference cycle: DocServer.callback
+            # has indirectly a reference to ServerThread.
+            self.docserver = None
+            self.serving = False
+            self.url = None
+
+    thread = ServerThread(urlhandler, hostname, port)
+    thread.start()
+    # Wait until thread.serving is True to make sure we are
+    # really up before returning.
+    while not thread.error and not thread.serving:
+        time.sleep(.01)
+    return thread
+
+
+def _url_handler(url, content_type="text/html"):
+    """The pydoc url handler for use with the pydoc server.
+
+    If the content_type is 'text/css', the _pydoc.css style
+    sheet is read and returned if it exits.
+
+    If the content_type is 'text/html', then the result of
+    get_html_page(url) is returned.
+    """
+    class _HTMLDoc(HTMLDoc):
+
+        def page(self, title, contents):
+            """Format an HTML page."""
+            css_path = "pydoc_data/_pydoc.css"
+            css_link = (
+                '<link rel="stylesheet" type="text/css" href="%s">' %
+                css_path)
+            return '''\
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
+<html><head><title>Pydoc: %s</title>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+%s</head><body bgcolor="#f0f0f8">%s<div style="clear:both;padding-top:.5em;">%s</div>
+</body></html>''' % (title, css_link, html_navbar(), contents)
+
+
+    html = _HTMLDoc()
+
+    def html_navbar():
+        version = html.escape("%s [%s, %s]" % (platform.python_version(),
+                                               platform.python_build()[0],
+                                               platform.python_compiler()))
+        return """
+            <div style='float:left'>
+                Python %s<br>%s
+            </div>
+            <div style='float:right'>
+                <div style='text-align:center'>
+                  <a href="index.html">Module Index</a>
+                  : <a href="topics.html">Topics</a>
+                  : <a href="keywords.html">Keywords</a>
+                </div>
+                <div>
+                    <form action="get" style='display:inline;'>
+                      <input type=text name=key size=15>
+                      <input type=submit value="Get">
+                    </form>&nbsp;
+                    <form action="search" style='display:inline;'>
+                      <input type=text name=key size=15>
+                      <input type=submit value="Search">
+                    </form>
+                </div>
+            </div>
+            """ % (version, html.escape(platform.platform(terse=True)))
+
+    def html_index():
+        """Module Index page."""
+
+        def bltinlink(name):
+            return '<a href="%s.html">%s</a>' % (name, name)
+
+        heading = html.heading(
+            '<big><big><strong>Index of Modules</strong></big></big>',
+            '#ffffff', '#7799ee')
+        names = [name for name in sys.builtin_module_names
+                 if name != '__main__']
+        contents = html.multicolumn(names, bltinlink)
+        contents = [heading, '<p>' + html.bigsection(
+            'Built-in Modules', '#ffffff', '#ee77aa', contents)]
+
+        seen = {}
+        for dir in sys.path:
+            contents.append(html.index(dir, seen))
+
+        contents.append(
+            '<p align=right><font color="#909090" face="helvetica,'
+            'arial"><strong>pydoc</strong> by Ka-Ping Yee'
+            '&lt;ping@lfw.org&gt;</font>')
+        return 'Index of Modules', ''.join(contents)
+
+    def html_search(key):
+        """Search results page."""
+        # scan for modules
+        search_result = []
+
+        def callback(path, modname, desc):
+            if modname[-9:] == '.__init__':
+                modname = modname[:-9] + ' (package)'
+            search_result.append((modname, desc and '- ' + desc))
+
+        with warnings.catch_warnings():
+            warnings.filterwarnings('ignore') # ignore problems during import
+            def onerror(modname):
+                pass
+            ModuleScanner().run(callback, key, onerror=onerror)
+
+        # format page
+        def bltinlink(name):
+            return '<a href="%s.html">%s</a>' % (name, name)
+
+        results = []
+        heading = html.heading(
+            '<big><big><strong>Search Results</strong></big></big>',
+            '#ffffff', '#7799ee')
+        for name, desc in search_result:
+            results.append(bltinlink(name) + desc)
+        contents = heading + html.bigsection(
+            'key = %s' % key, '#ffffff', '#ee77aa', '<br>'.join(results))
+        return 'Search Results', contents
+
+    def html_topics():
+        """Index of topic texts available."""
+
+        def bltinlink(name):
+            return '<a href="topic?key=%s">%s</a>' % (name, name)
+
+        heading = html.heading(
+            '<big><big><strong>INDEX</strong></big></big>',
+            '#ffffff', '#7799ee')
+        names = sorted(Helper.topics.keys())
+
+        contents = html.multicolumn(names, bltinlink)
+        contents = heading + html.bigsection(
+            'Topics', '#ffffff', '#ee77aa', contents)
+        return 'Topics', contents
+
+    def html_keywords():
+        """Index of keywords."""
+        heading = html.heading(
+            '<big><big><strong>INDEX</strong></big></big>',
+            '#ffffff', '#7799ee')
+        names = sorted(Helper.keywords.keys())
+
+        def bltinlink(name):
+            return '<a href="topic?key=%s">%s</a>' % (name, name)
+
+        contents = html.multicolumn(names, bltinlink)
+        contents = heading + html.bigsection(
+            'Keywords', '#ffffff', '#ee77aa', contents)
+        return 'Keywords', contents
+
+    def html_topicpage(topic):
+        """Topic or keyword help page."""
+        buf = io.StringIO()
+        htmlhelp = Helper(buf, buf)
+        contents, xrefs = htmlhelp._gettopic(topic)
+        if topic in htmlhelp.keywords:
+            title = 'KEYWORD'
+        else:
+            title = 'TOPIC'
+        heading = html.heading(
+            '<big><big><strong>%s</strong></big></big>' % title,
+            '#ffffff', '#7799ee')
+        contents = '<pre>%s</pre>' % html.markup(contents)
+        contents = html.bigsection(topic , '#ffffff','#ee77aa', contents)
+        if xrefs:
+            xrefs = sorted(xrefs.split())
+
+            def bltinlink(name):
+                return '<a href="topic?key=%s">%s</a>' % (name, name)
+
+            xrefs = html.multicolumn(xrefs, bltinlink)
+            xrefs = html.section('Related help topics: ',
+                                 '#ffffff', '#ee77aa', xrefs)
+        return ('%s %s' % (title, topic),
+                ''.join((heading, contents, xrefs)))
+
+    def html_getobj(url):
+        obj = locate(url, forceload=1)
+        if obj is None and url != 'None':
+            raise ValueError('could not find object')
+        title = describe(obj)
+        content = html.document(obj, url)
+        return title, content
+
+    def html_error(url, exc):
+        heading = html.heading(
+            '<big><big><strong>Error</strong></big></big>',
+            '#ffffff', '#7799ee')
+        contents = '<br>'.join(html.escape(line) for line in
+                               format_exception_only(type(exc), exc))
+        contents = heading + html.bigsection(url, '#ffffff', '#bb0000',
+                                             contents)
+        return "Error - %s" % url, contents
+
+    def get_html_page(url):
+        """Generate an HTML page for url."""
+        complete_url = url
+        if url.endswith('.html'):
+            url = url[:-5]
+        try:
+            if url in ("", "index"):
+                title, content = html_index()
+            elif url == "topics":
+                title, content = html_topics()
+            elif url == "keywords":
+                title, content = html_keywords()
+            elif '=' in url:
+                op, _, url = url.partition('=')
+                if op == "search?key":
+                    title, content = html_search(url)
+                elif op == "topic?key":
+                    # try topics first, then objects.
+                    try:
+                        title, content = html_topicpage(url)
+                    except ValueError:
+                        title, content = html_getobj(url)
+                elif op == "get?key":
+                    # try objects first, then topics.
+                    if url in ("", "index"):
+                        title, content = html_index()
+                    else:
+                        try:
+                            title, content = html_getobj(url)
+                        except ValueError:
+                            title, content = html_topicpage(url)
+                else:
+                    raise ValueError('bad pydoc url')
+            else:
+                title, content = html_getobj(url)
+        except Exception as exc:
+            # Catch any errors and display them in an error page.
+            title, content = html_error(complete_url, exc)
+        return html.page(title, content)
+
+    if url.startswith('/'):
+        url = url[1:]
+    if content_type == 'text/css':
+        path_here = os.path.dirname(os.path.realpath(__file__))
+        css_path = os.path.join(path_here, url)
+        with open(css_path) as fp:
+            return ''.join(fp.readlines())
+    elif content_type == 'text/html':
+        return get_html_page(url)
+    # Errors outside the url handler are caught by the server.
+    raise TypeError('unknown content type %r for url %s' % (content_type, url))
+
+
+def browse(port=0, *, open_browser=True, hostname='localhost'):
+    """Start the enhanced pydoc Web server and open a Web browser.
+
+    Use port '0' to start the server on an arbitrary port.
+    Set open_browser to False to suppress opening a browser.
+    """
+    import webbrowser
+    serverthread = _start_server(_url_handler, hostname, port)
+    if serverthread.error:
+        print(serverthread.error)
+        return
+    if serverthread.serving:
+        server_help_msg = 'Server commands: [b]rowser, [q]uit'
+        if open_browser:
+            webbrowser.open(serverthread.url)
+        try:
+            print('Server ready at', serverthread.url)
+            print(server_help_msg)
+            while serverthread.serving:
+                cmd = input('server> ')
+                cmd = cmd.lower()
+                if cmd == 'q':
+                    break
+                elif cmd == 'b':
+                    webbrowser.open(serverthread.url)
+                else:
+                    print(server_help_msg)
+        except (KeyboardInterrupt, EOFError):
+            print()
+        finally:
+            if serverthread.serving:
+                serverthread.stop()
+                print('Server stopped')
+
+
+# -------------------------------------------------- command-line interface
+
+def ispath(x):
+    return isinstance(x, str) and x.find(os.sep) >= 0
+
+def _get_revised_path(given_path, argv0):
+    """Ensures current directory is on returned path, and argv0 directory is not
+
+    Exception: argv0 dir is left alone if it's also pydoc's directory.
+
+    Returns a new path entry list, or None if no adjustment is needed.
+    """
+    # Scripts may get the current directory in their path by default if they're
+    # run with the -m switch, or directly from the current directory.
+    # The interactive prompt also allows imports from the current directory.
+
+    # Accordingly, if the current directory is already present, don't make
+    # any changes to the given_path
+    if '' in given_path or os.curdir in given_path or os.getcwd() in given_path:
+        return None
+
+    # Otherwise, add the current directory to the given path, and remove the
+    # script directory (as long as the latter isn't also pydoc's directory.
+    stdlib_dir = os.path.dirname(__file__)
+    script_dir = os.path.dirname(argv0)
+    revised_path = given_path.copy()
+    if script_dir in given_path and not os.path.samefile(script_dir, stdlib_dir):
+        revised_path.remove(script_dir)
+    revised_path.insert(0, os.getcwd())
+    return revised_path
+
+
+# Note: the tests only cover _get_revised_path, not _adjust_cli_path itself
+def _adjust_cli_sys_path():
+    """Ensures current directory is on sys.path, and __main__ directory is not.
+
+    Exception: __main__ dir is left alone if it's also pydoc's directory.
+    """
+    revised_path = _get_revised_path(sys.path, sys.argv[0])
+    if revised_path is not None:
+        sys.path[:] = revised_path
+
+
+def cli():
+    """Command-line interface (looks at sys.argv to decide what to do)."""
+    import getopt
+    class BadUsage(Exception): pass
+
+    _adjust_cli_sys_path()
+
+    try:
+        opts, args = getopt.getopt(sys.argv[1:], 'bk:n:p:w')
+        writing = False
+        start_server = False
+        open_browser = False
+        port = 0
+        hostname = 'localhost'
+        for opt, val in opts:
+            if opt == '-b':
+                start_server = True
+                open_browser = True
+            if opt == '-k':
+                apropos(val)
+                return
+            if opt == '-p':
+                start_server = True
+                port = val
+            if opt == '-w':
+                writing = True
+            if opt == '-n':
+                start_server = True
+                hostname = val
+
+        if start_server:
+            browse(port, hostname=hostname, open_browser=open_browser)
+            return
+
+        if not args: raise BadUsage
+        for arg in args:
+            if ispath(arg) and not os.path.exists(arg):
+                print('file %r does not exist' % arg)
+                break
+            try:
+                if ispath(arg) and os.path.isfile(arg):
+                    arg = importfile(arg)
+                if writing:
+                    if ispath(arg) and os.path.isdir(arg):
+                        writedocs(arg)
+                    else:
+                        writedoc(arg)
+                else:
+                    help.help(arg)
+            except ErrorDuringImport as value:
+                print(value)
+
+    except (getopt.error, BadUsage):
+        cmd = os.path.splitext(os.path.basename(sys.argv[0]))[0]
+        print("""pydoc - the Python documentation tool
+
+{cmd} <name> ...
+    Show text documentation on something.  <name> may be the name of a
+    Python keyword, topic, function, module, or package, or a dotted
+    reference to a class or function within a module or module in a
+    package.  If <name> contains a '{sep}', it is used as the path to a
+    Python source file to document. If name is 'keywords', 'topics',
+    or 'modules', a listing of these things is displayed.
+
+{cmd} -k <keyword>
+    Search for a keyword in the synopsis lines of all available modules.
+
+{cmd} -n <hostname>
+    Start an HTTP server with the given hostname (default: localhost).
+
+{cmd} -p <port>
+    Start an HTTP server on the given port on the local machine.  Port
+    number 0 can be used to get an arbitrary unused port.
+
+{cmd} -b
+    Start an HTTP server on an arbitrary unused port and open a Web browser
+    to interactively browse documentation.  This option can be used in
+    combination with -n and/or -p.
+
+{cmd} -w <name> ...
+    Write out the HTML documentation for a module to a file in the current
+    directory.  If <name> contains a '{sep}', it is treated as a filename; if
+    it names a directory, documentation is written for all the contents.
+""".format(cmd=cmd, sep=os.sep))
+
+if __name__ == '__main__':
+    cli()