add ydb deps

8 files changed, 928 insertions, 0 deletions

diff --git a/contrib/python/ipython/py2/IPython/external/__init__.py b/contrib/python/ipython/py2/IPython/external/__init__.py
new file mode 100644
index 0000000000..3104c19462
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/__init__.py
@@ -0,0 +1,5 @@
+"""
+This package contains all third-party modules bundled with IPython.
+"""
+
+__all__ = ["simplegeneric"]
diff --git a/contrib/python/ipython/py2/IPython/external/decorators/__init__.py b/contrib/python/ipython/py2/IPython/external/decorators/__init__.py
new file mode 100644
index 0000000000..dd8f52b711
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/decorators/__init__.py
@@ -0,0 +1,9 @@
+try:
+    from numpy.testing.decorators import *
+    from numpy.testing.noseclasses import KnownFailure
+except ImportError:
+    from ._decorators import *
+    try:
+        from ._numpy_testing_noseclasses import KnownFailure
+    except ImportError:
+        pass
diff --git a/contrib/python/ipython/py2/IPython/external/decorators/_decorators.py b/contrib/python/ipython/py2/IPython/external/decorators/_decorators.py
new file mode 100644
index 0000000000..19de5e5cde
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/decorators/_decorators.py
@@ -0,0 +1,281 @@
+"""
+Decorators for labeling and modifying behavior of test objects.
+
+Decorators that merely return a modified version of the original
+function object are straightforward. Decorators that return a new
+function object need to use
+::
+
+  nose.tools.make_decorator(original_function)(decorator)
+
+in returning the decorator, in order to preserve meta-data such as
+function name, setup and teardown functions and so on - see
+``nose.tools`` for more information.
+
+"""
+import warnings
+
+# IPython changes: make this work if numpy not available
+# Original code:
+#from numpy.testing.utils import \
+#        WarningManager, WarningMessage
+# Our version:
+from ._numpy_testing_utils import WarningManager
+try:
+    from ._numpy_testing_noseclasses import KnownFailureTest
+except:
+    pass
+
+# End IPython changes
+
+def slow(t):
+    """
+    Label a test as 'slow'.
+
+    The exact definition of a slow test is obviously both subjective and
+    hardware-dependent, but in general any individual test that requires more
+    than a second or two should be labeled as slow (the whole suite consists of
+    thousands of tests, so even a second is significant).
+
+    Parameters
+    ----------
+    t : callable
+        The test to label as slow.
+
+    Returns
+    -------
+    t : callable
+        The decorated test `t`.
+
+    Examples
+    --------
+    The `numpy.testing` module includes ``import decorators as dec``.
+    A test can be decorated as slow like this::
+
+      from numpy.testing import *
+
+      @dec.slow
+      def test_big(self):
+          print 'Big, slow test'
+
+    """
+
+    t.slow = True
+    return t
+
+def setastest(tf=True):
+    """
+    Signals to nose that this function is or is not a test.
+
+    Parameters
+    ----------
+    tf : bool
+        If True, specifies that the decorated callable is a test.
+        If False, specifies that the decorated callable is not a test.
+        Default is True.
+
+    Notes
+    -----
+    This decorator can't use the nose namespace, because it can be
+    called from a non-test module. See also ``istest`` and ``nottest`` in
+    ``nose.tools``.
+
+    Examples
+    --------
+    `setastest` can be used in the following way::
+
+      from numpy.testing.decorators import setastest
+
+      @setastest(False)
+      def func_with_test_in_name(arg1, arg2):
+          pass
+
+    """
+    def set_test(t):
+        t.__test__ = tf
+        return t
+    return set_test
+
+def skipif(skip_condition, msg=None):
+    """
+    Make function raise SkipTest exception if a given condition is true.
+
+    If the condition is a callable, it is used at runtime to dynamically
+    make the decision. This is useful for tests that may require costly
+    imports, to delay the cost until the test suite is actually executed.
+
+    Parameters
+    ----------
+    skip_condition : bool or callable
+        Flag to determine whether to skip the decorated test.
+    msg : str, optional
+        Message to give on raising a SkipTest exception. Default is None.
+
+    Returns
+    -------
+    decorator : function
+        Decorator which, when applied to a function, causes SkipTest
+        to be raised when `skip_condition` is True, and the function
+        to be called normally otherwise.
+
+    Notes
+    -----
+    The decorator itself is decorated with the ``nose.tools.make_decorator``
+    function in order to transmit function name, and various other metadata.
+
+    """
+
+    def skip_decorator(f):
+        # Local import to avoid a hard nose dependency and only incur the
+        # import time overhead at actual test-time.
+        import nose
+
+        # Allow for both boolean or callable skip conditions.
+        if callable(skip_condition):
+            skip_val = lambda : skip_condition()
+        else:
+            skip_val = lambda : skip_condition
+
+        def get_msg(func,msg=None):
+            """Skip message with information about function being skipped."""
+            if msg is None:
+                out = 'Test skipped due to test condition'
+            else:
+                out = '\n'+msg
+
+            return "Skipping test: %s%s" % (func.__name__,out)
+
+        # We need to define *two* skippers because Python doesn't allow both
+        # return with value and yield inside the same function.
+        def skipper_func(*args, **kwargs):
+            """Skipper for normal test functions."""
+            if skip_val():
+                raise nose.SkipTest(get_msg(f,msg))
+            else:
+                return f(*args, **kwargs)
+
+        def skipper_gen(*args, **kwargs):
+            """Skipper for test generators."""
+            if skip_val():
+                raise nose.SkipTest(get_msg(f,msg))
+            else:
+                for x in f(*args, **kwargs):
+                    yield x
+
+        # Choose the right skipper to use when building the actual decorator.
+        if nose.util.isgenerator(f):
+            skipper = skipper_gen
+        else:
+            skipper = skipper_func
+
+        return nose.tools.make_decorator(f)(skipper)
+
+    return skip_decorator
+
+def knownfailureif(fail_condition, msg=None):
+    """
+    Make function raise KnownFailureTest exception if given condition is true.
+
+    If the condition is a callable, it is used at runtime to dynamically
+    make the decision. This is useful for tests that may require costly
+    imports, to delay the cost until the test suite is actually executed.
+
+    Parameters
+    ----------
+    fail_condition : bool or callable
+        Flag to determine whether to mark the decorated test as a known
+        failure (if True) or not (if False).
+    msg : str, optional
+        Message to give on raising a KnownFailureTest exception.
+        Default is None.
+
+    Returns
+    -------
+    decorator : function
+        Decorator, which, when applied to a function, causes SkipTest
+        to be raised when `skip_condition` is True, and the function
+        to be called normally otherwise.
+
+    Notes
+    -----
+    The decorator itself is decorated with the ``nose.tools.make_decorator``
+    function in order to transmit function name, and various other metadata.
+
+    """
+    if msg is None:
+        msg = 'Test skipped due to known failure'
+
+    # Allow for both boolean or callable known failure conditions.
+    if callable(fail_condition):
+        fail_val = lambda : fail_condition()
+    else:
+        fail_val = lambda : fail_condition
+
+    def knownfail_decorator(f):
+        # Local import to avoid a hard nose dependency and only incur the
+        # import time overhead at actual test-time.
+        import nose
+        def knownfailer(*args, **kwargs):
+            if fail_val():
+                raise KnownFailureTest(msg)
+            else:
+                return f(*args, **kwargs)
+        return nose.tools.make_decorator(f)(knownfailer)
+
+    return knownfail_decorator
+
+def deprecated(conditional=True):
+    """
+    Filter deprecation warnings while running the test suite.
+
+    This decorator can be used to filter DeprecationWarning's, to avoid
+    printing them during the test suite run, while checking that the test
+    actually raises a DeprecationWarning.
+
+    Parameters
+    ----------
+    conditional : bool or callable, optional
+        Flag to determine whether to mark test as deprecated or not. If the
+        condition is a callable, it is used at runtime to dynamically make the
+        decision. Default is True.
+
+    Returns
+    -------
+    decorator : function
+        The `deprecated` decorator itself.
+
+    Notes
+    -----
+    .. versionadded:: 1.4.0
+
+    """
+    def deprecate_decorator(f):
+        # Local import to avoid a hard nose dependency and only incur the
+        # import time overhead at actual test-time.
+        import nose
+
+        def _deprecated_imp(*args, **kwargs):
+            # Poor man's replacement for the with statement
+            ctx = WarningManager(record=True)
+            l = ctx.__enter__()
+            warnings.simplefilter('always')
+            try:
+                f(*args, **kwargs)
+                if not len(l) > 0:
+                    raise AssertionError("No warning raised when calling %s"
+                            % f.__name__)
+                if not l[0].category is DeprecationWarning:
+                    raise AssertionError("First warning for %s is not a " \
+                            "DeprecationWarning( is %s)" % (f.__name__, l[0]))
+            finally:
+                ctx.__exit__()
+
+        if callable(conditional):
+            cond = conditional()
+        else:
+            cond = conditional
+        if cond:
+            return nose.tools.make_decorator(f)(_deprecated_imp)
+        else:
+            return f
+    return deprecate_decorator
diff --git a/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_noseclasses.py b/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_noseclasses.py
new file mode 100644
index 0000000000..ca6ccd87bb
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_noseclasses.py
@@ -0,0 +1,41 @@
+# IPython: modified copy of numpy.testing.noseclasses, so
+# IPython.external._decorators works without numpy being installed.
+
+# These classes implement a "known failure" error class.
+
+import os
+
+from nose.plugins.errorclass import ErrorClass, ErrorClassPlugin
+
+class KnownFailureTest(Exception):
+    '''Raise this exception to mark a test as a known failing test.'''
+    pass
+
+
+class KnownFailure(ErrorClassPlugin):
+    '''Plugin that installs a KNOWNFAIL error class for the
+    KnownFailureClass exception.  When KnownFailureTest is raised,
+    the exception will be logged in the knownfail attribute of the
+    result, 'K' or 'KNOWNFAIL' (verbose) will be output, and the
+    exception will not be counted as an error or failure.'''
+    enabled = True
+    knownfail = ErrorClass(KnownFailureTest,
+                           label='KNOWNFAIL',
+                           isfailure=False)
+
+    def options(self, parser, env=os.environ):
+        env_opt = 'NOSE_WITHOUT_KNOWNFAIL'
+        parser.add_option('--no-knownfail', action='store_true',
+                          dest='noKnownFail', default=env.get(env_opt, False),
+                          help='Disable special handling of KnownFailureTest '
+                               'exceptions')
+
+    def configure(self, options, conf):
+        if not self.can_configure:
+            return
+        self.conf = conf
+        disable = getattr(options, 'noKnownFail', False)
+        if disable:
+            self.enabled = False
+
+
diff --git a/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_utils.py b/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_utils.py
new file mode 100644
index 0000000000..ad7bd0f981
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/decorators/_numpy_testing_utils.py
@@ -0,0 +1,112 @@
+# IPython: modified copy of numpy.testing.utils, so
+# IPython.external._decorators works without numpy being installed.
+"""
+Utility function to facilitate testing.
+"""
+
+import sys
+import warnings
+
+# The following two classes are copied from python 2.6 warnings module (context
+# manager)
+class WarningMessage(object):
+
+    """
+    Holds the result of a single showwarning() call.
+
+    Notes
+    -----
+    `WarningMessage` is copied from the Python 2.6 warnings module,
+    so it can be used in NumPy with older Python versions.
+
+    """
+
+    _WARNING_DETAILS = ("message", "category", "filename", "lineno", "file",
+                        "line")
+
+    def __init__(self, message, category, filename, lineno, file=None,
+                    line=None):
+        local_values = locals()
+        for attr in self._WARNING_DETAILS:
+            setattr(self, attr, local_values[attr])
+        if category:
+            self._category_name = category.__name__
+        else:
+            self._category_name = None
+
+    def __str__(self):
+        return ("{message : %r, category : %r, filename : %r, lineno : %s, "
+                    "line : %r}" % (self.message, self._category_name,
+                                    self.filename, self.lineno, self.line))
+
+class WarningManager:
+    """
+    A context manager that copies and restores the warnings filter upon
+    exiting the context.
+
+    The 'record' argument specifies whether warnings should be captured by a
+    custom implementation of ``warnings.showwarning()`` and be appended to a
+    list returned by the context manager. Otherwise None is returned by the
+    context manager. The objects appended to the list are arguments whose
+    attributes mirror the arguments to ``showwarning()``.
+
+    The 'module' argument is to specify an alternative module to the module
+    named 'warnings' and imported under that name. This argument is only useful
+    when testing the warnings module itself.
+
+    Notes
+    -----
+    `WarningManager` is a copy of the ``catch_warnings`` context manager
+    from the Python 2.6 warnings module, with slight modifications.
+    It is copied so it can be used in NumPy with older Python versions.
+
+    """
+    def __init__(self, record=False, module=None):
+        self._record = record
+        if module is None:
+            self._module = sys.modules['warnings']
+        else:
+            self._module = module
+        self._entered = False
+
+    def __enter__(self):
+        if self._entered:
+            raise RuntimeError("Cannot enter %r twice" % self)
+        self._entered = True
+        self._filters = self._module.filters
+        self._module.filters = self._filters[:]
+        self._showwarning = self._module.showwarning
+        if self._record:
+            log = []
+            def showwarning(*args, **kwargs):
+                log.append(WarningMessage(*args, **kwargs))
+            self._module.showwarning = showwarning
+            return log
+        else:
+            return None
+
+    def __exit__(self, type_, value, traceback):
+        if not self._entered:
+            raise RuntimeError("Cannot exit %r without entering first" % self)
+        self._module.filters = self._filters
+        self._module.showwarning = self._showwarning
+
+def assert_warns(warning_class, func, *args, **kw):
+    """Fail unless a warning of class warning_class is thrown by callable when
+    invoked with arguments args and keyword arguments kwargs.
+    
+    If a different type of warning is thrown, it will not be caught, and the
+    test case will be deemed to have suffered an error.
+    """
+
+    # XXX: once we may depend on python >= 2.6, this can be replaced by the
+    # warnings module context manager.
+    with WarningManager(record=True) as l:
+        warnings.simplefilter('always')
+        func(*args, **kw)
+        if not len(l) > 0:
+            raise AssertionError("No warning raised when calling %s"
+                    % func.__name__)
+        if not l[0].category is warning_class:
+            raise AssertionError("First warning for %s is not a " \
+                    "%s( is %s)" % (func.__name__, warning_class, l[0]))
diff --git a/contrib/python/ipython/py2/IPython/external/mathjax.py b/contrib/python/ipython/py2/IPython/external/mathjax.py
new file mode 100644
index 0000000000..1b9b80905b
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/mathjax.py
@@ -0,0 +1,13 @@
+#!/usr/bin/python
+"""
+`IPython.external.mathjax` is deprecated with IPython 4.0+
+
+mathjax is now install by default with the notebook package
+
+"""
+
+import sys 
+
+if __name__ == '__main__' :
+    sys.exit("IPython.external.mathjax is deprecated, Mathjax is now installed by default with the notebook package")
+
diff --git a/contrib/python/ipython/py2/IPython/external/qt_for_kernel.py b/contrib/python/ipython/py2/IPython/external/qt_for_kernel.py
new file mode 100644
index 0000000000..1a94e7e0a2
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/qt_for_kernel.py
@@ -0,0 +1,95 @@
+""" Import Qt in a manner suitable for an IPython kernel.
+
+This is the import used for the `gui=qt` or `matplotlib=qt` initialization.
+
+Import Priority:
+
+if Qt has been imported anywhere else:
+   use that
+
+if matplotlib has been imported and doesn't support v2 (<= 1.0.1):
+    use PyQt4 @v1
+
+Next, ask QT_API env variable
+
+if QT_API not set:
+    ask matplotlib what it's using. If Qt4Agg or Qt5Agg, then use the
+        version matplotlib is configured with
+
+    else: (matplotlib said nothing)
+        # this is the default path - nobody told us anything
+        try in this order:
+            PyQt default version, PySide, PyQt5
+else:
+    use what QT_API says
+
+"""
+# NOTE: This is no longer an external, third-party module, and should be
+# considered part of IPython. For compatibility however, it is being kept in
+# IPython/external.
+
+import os
+import sys
+
+from IPython.utils.version import check_version
+from IPython.external.qt_loaders import (load_qt, loaded_api, QT_API_PYSIDE,
+                                         QT_API_PYSIDE2, QT_API_PYQT, QT_API_PYQT5,
+                                         QT_API_PYQTv1, QT_API_PYQT_DEFAULT)
+
+_qt_apis = (QT_API_PYSIDE, QT_API_PYSIDE2, QT_API_PYQT, QT_API_PYQT5, QT_API_PYQTv1,
+            QT_API_PYQT_DEFAULT)
+
+#Constraints placed on an imported matplotlib
+def matplotlib_options(mpl):
+    if mpl is None:
+        return
+    backend = mpl.rcParams.get('backend', None)
+    if backend == 'Qt4Agg':
+        mpqt = mpl.rcParams.get('backend.qt4', None)
+        if mpqt is None:
+            return None
+        if mpqt.lower() == 'pyside':
+            return [QT_API_PYSIDE]
+        elif mpqt.lower() == 'pyqt4':
+            return [QT_API_PYQT_DEFAULT]
+        elif mpqt.lower() == 'pyqt4v2':
+            return [QT_API_PYQT]
+        raise ImportError("unhandled value for backend.qt4 from matplotlib: %r" %
+                          mpqt)
+    elif backend == 'Qt5Agg':
+        mpqt = mpl.rcParams.get('backend.qt5', None)
+        if mpqt is None:
+            return None
+        if mpqt.lower() == 'pyqt5':
+            return [QT_API_PYQT5]
+        raise ImportError("unhandled value for backend.qt5 from matplotlib: %r" %
+                          mpqt)
+
+def get_options():
+    """Return a list of acceptable QT APIs, in decreasing order of
+    preference
+    """
+    #already imported Qt somewhere. Use that
+    loaded = loaded_api()
+    if loaded is not None:
+        return [loaded]
+
+    mpl = sys.modules.get('matplotlib', None)
+
+    if mpl is not None and not check_version(mpl.__version__, '1.0.2'):
+        #1.0.1 only supports PyQt4 v1
+        return [QT_API_PYQT_DEFAULT]
+
+    qt_api = os.environ.get('QT_API', None)
+    if qt_api is None:
+        #no ETS variable. Ask mpl, then use default fallback path
+        return matplotlib_options(mpl) or [QT_API_PYQT_DEFAULT, QT_API_PYSIDE,
+                                           QT_API_PYQT5, QT_API_PYSIDE2]
+    elif qt_api not in _qt_apis:
+        raise RuntimeError("Invalid Qt API %r, valid values are: %r" %
+                           (qt_api, ', '.join(_qt_apis)))
+    else:
+        return [qt_api]
+
+api_opts = get_options()
+QtCore, QtGui, QtSvg, QT_API = load_qt(api_opts)
diff --git a/contrib/python/ipython/py2/IPython/external/qt_loaders.py b/contrib/python/ipython/py2/IPython/external/qt_loaders.py
new file mode 100644
index 0000000000..3b894fb2ab
--- /dev/null
+++ b/contrib/python/ipython/py2/IPython/external/qt_loaders.py
@@ -0,0 +1,372 @@
+"""
+This module contains factory functions that attempt
+to return Qt submodules from the various python Qt bindings.
+
+It also protects against double-importing Qt with different
+bindings, which is unstable and likely to crash
+
+This is used primarily by qt and qt_for_kernel, and shouldn't
+be accessed directly from the outside
+"""
+import sys
+import types
+from functools import partial
+
+from IPython.utils.version import check_version
+
+# Available APIs.
+QT_API_PYQT = 'pyqt' # Force version 2
+QT_API_PYQT5 = 'pyqt5'
+QT_API_PYQTv1 = 'pyqtv1' # Force version 2
+QT_API_PYQT_DEFAULT = 'pyqtdefault' # use system default for version 1 vs. 2
+QT_API_PYSIDE = 'pyside'
+QT_API_PYSIDE2 = 'pyside2'
+
+api_to_module = {QT_API_PYSIDE2: 'PySide2',
+                 QT_API_PYSIDE: 'PySide',
+                 QT_API_PYQT: 'PyQt4',
+                 QT_API_PYQTv1: 'PyQt4',
+                 QT_API_PYQT5: 'PyQt5',
+                 QT_API_PYQT_DEFAULT: 'PyQt4',
+                }
+
+
+class ImportDenier(object):
+    """Import Hook that will guard against bad Qt imports
+    once IPython commits to a specific binding
+    """
+
+    def __init__(self):
+        self.__forbidden = set()
+
+    def forbid(self, module_name):
+        sys.modules.pop(module_name, None)
+        self.__forbidden.add(module_name)
+
+    def find_module(self, fullname, path=None):
+        if path:
+            return
+        if fullname in self.__forbidden:
+            return self
+
+    def load_module(self, fullname):
+        raise ImportError("""
+    Importing %s disabled by IPython, which has
+    already imported an Incompatible QT Binding: %s
+    """ % (fullname, loaded_api()))
+
+ID = ImportDenier()
+sys.meta_path.insert(0, ID)
+
+
+def commit_api(api):
+    """Commit to a particular API, and trigger ImportErrors on subsequent
+       dangerous imports"""
+
+    if api == QT_API_PYSIDE2:
+        ID.forbid('PySide')
+        ID.forbid('PyQt4')
+        ID.forbid('PyQt5')
+    if api == QT_API_PYSIDE:
+        ID.forbid('PySide2')
+        ID.forbid('PyQt4')
+        ID.forbid('PyQt5')
+    elif api == QT_API_PYQT5:
+        ID.forbid('PySide2')
+        ID.forbid('PySide')
+        ID.forbid('PyQt4')
+    else:   # There are three other possibilities, all representing PyQt4
+        ID.forbid('PyQt5')
+        ID.forbid('PySide2')
+        ID.forbid('PySide')
+
+
+def loaded_api():
+    """Return which API is loaded, if any
+
+    If this returns anything besides None,
+    importing any other Qt binding is unsafe.
+
+    Returns
+    -------
+    None, 'pyside2', 'pyside', 'pyqt', 'pyqt5', or 'pyqtv1'
+    """
+    if 'PyQt4.QtCore' in sys.modules:
+        if qtapi_version() == 2:
+            return QT_API_PYQT
+        else:
+            return QT_API_PYQTv1
+    elif 'PySide.QtCore' in sys.modules:
+        return QT_API_PYSIDE
+    elif 'PySide2.QtCore' in sys.modules:
+        return QT_API_PYSIDE2
+    elif 'PyQt5.QtCore' in sys.modules:
+        return QT_API_PYQT5
+    return None
+
+
+def has_binding(api):
+    """Safely check for PyQt4/5, PySide or PySide2, without importing submodules
+
+    Supports Python <= 3.3
+
+       Parameters
+       ----------
+       api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyside2' | 'pyqtdefault']
+            Which module to check for
+
+       Returns
+       -------
+       True if the relevant module appears to be importable
+    """
+    # we can't import an incomplete pyside and pyqt4
+    # this will cause a crash in sip (#1431)
+    # check for complete presence before importing
+    module_name = api_to_module[api]
+
+    import imp
+    try:
+        #importing top level PyQt4/PySide module is ok...
+        mod = __import__(module_name)
+        #...importing submodules is not
+        imp.find_module('QtCore', mod.__path__)
+        imp.find_module('QtGui', mod.__path__)
+        imp.find_module('QtSvg', mod.__path__)
+        if api in (QT_API_PYQT5, QT_API_PYSIDE2):
+            # QT5 requires QtWidgets too
+            imp.find_module('QtWidgets', mod.__path__)
+
+        #we can also safely check PySide version
+        if api == QT_API_PYSIDE:
+            return check_version(mod.__version__, '1.0.3')
+        else:
+            return True
+    except ImportError:
+        return False
+
+def has_binding_new(api):
+    """Safely check for PyQt4/5, PySide or PySide2, without importing submodules
+
+    Supports Python >= 3.4
+
+        Parameters
+        ----------
+        api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyside2' | 'pyqtdefault']
+             Which module to check for
+
+        Returns
+        -------
+        True if the relevant module appears to be importable
+     """
+    module_name = api_to_module[api]
+    from importlib.util import find_spec
+
+    required = ['QtCore', 'QtGui', 'QtSvg']
+    if api in (QT_API_PYQT5, QT_API_PYSIDE2):
+        # QT5 requires QtWidgets too
+        required.append('QtWidgets')
+
+    for submod in required:
+        try:
+            spec = find_spec('%s.%s' % (module_name, submod))
+        except ImportError:
+            # Package (e.g. PyQt5) not found
+            return False
+        else:
+            if spec is None:
+                # Submodule (e.g. PyQt5.QtCore) not found
+                return False
+
+    if api == QT_API_PYSIDE:
+        # We can also safely check PySide version
+        import PySide
+        return check_version(PySide.__version__, '1.0.3')
+
+    return True
+
+if sys.version_info >= (3, 4):
+    has_binding = has_binding_new
+
+def qtapi_version():
+    """Return which QString API has been set, if any
+
+    Returns
+    -------
+    The QString API version (1 or 2), or None if not set
+    """
+    try:
+        import sip
+    except ImportError:
+        return
+    try:
+        return sip.getapi('QString')
+    except ValueError:
+        return
+
+
+def can_import(api):
+    """Safely query whether an API is importable, without importing it"""
+    if not has_binding(api):
+        return False
+
+    current = loaded_api()
+    if api == QT_API_PYQT_DEFAULT:
+        return current in [QT_API_PYQT, QT_API_PYQTv1, None]
+    else:
+        return current in [api, None]
+
+
+def import_pyqt4(version=2):
+    """
+    Import PyQt4
+
+    Parameters
+    ----------
+    version : 1, 2, or None
+      Which QString/QVariant API to use. Set to None to use the system
+      default
+
+    ImportErrors rasied within this function are non-recoverable
+    """
+    # The new-style string API (version=2) automatically
+    # converts QStrings to Unicode Python strings. Also, automatically unpacks
+    # QVariants to their underlying objects.
+    import sip
+
+    if version is not None:
+        sip.setapi('QString', version)
+        sip.setapi('QVariant', version)
+
+    from PyQt4 import QtGui, QtCore, QtSvg
+
+    if not check_version(QtCore.PYQT_VERSION_STR, '4.7'):
+        raise ImportError("IPython requires PyQt4 >= 4.7, found %s" %
+                          QtCore.PYQT_VERSION_STR)
+
+    # Alias PyQt-specific functions for PySide compatibility.
+    QtCore.Signal = QtCore.pyqtSignal
+    QtCore.Slot = QtCore.pyqtSlot
+
+    # query for the API version (in case version == None)
+    version = sip.getapi('QString')
+    api = QT_API_PYQTv1 if version == 1 else QT_API_PYQT
+    return QtCore, QtGui, QtSvg, api
+
+
+def import_pyqt5():
+    """
+    Import PyQt5
+
+    ImportErrors rasied within this function are non-recoverable
+    """
+    import sip
+
+    from PyQt5 import QtCore, QtSvg, QtWidgets, QtGui
+
+    # Alias PyQt-specific functions for PySide compatibility.
+    QtCore.Signal = QtCore.pyqtSignal
+    QtCore.Slot = QtCore.pyqtSlot
+
+    # Join QtGui and QtWidgets for Qt4 compatibility.
+    QtGuiCompat = types.ModuleType('QtGuiCompat')
+    QtGuiCompat.__dict__.update(QtGui.__dict__)
+    QtGuiCompat.__dict__.update(QtWidgets.__dict__)
+
+    api = QT_API_PYQT5
+    return QtCore, QtGuiCompat, QtSvg, api
+
+
+def import_pyside():
+    """
+    Import PySide
+
+    ImportErrors raised within this function are non-recoverable
+    """
+    from PySide import QtGui, QtCore, QtSvg
+    return QtCore, QtGui, QtSvg, QT_API_PYSIDE
+
+def import_pyside2():
+    """
+    Import PySide2
+
+    ImportErrors raised within this function are non-recoverable
+    """
+    from PySide2 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
+
+    # Join QtGui and QtWidgets for Qt4 compatibility.
+    QtGuiCompat = types.ModuleType('QtGuiCompat')
+    QtGuiCompat.__dict__.update(QtGui.__dict__)
+    QtGuiCompat.__dict__.update(QtWidgets.__dict__)
+    QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
+
+    return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE2
+
+
+def load_qt(api_options):
+    """
+    Attempt to import Qt, given a preference list
+    of permissible bindings
+
+    It is safe to call this function multiple times.
+
+    Parameters
+    ----------
+    api_options: List of strings
+        The order of APIs to try. Valid items are 'pyside', 'pyside2',
+        'pyqt', 'pyqt5', 'pyqtv1' and 'pyqtdefault'
+
+    Returns
+    -------
+
+    A tuple of QtCore, QtGui, QtSvg, QT_API
+    The first three are the Qt modules. The last is the
+    string indicating which module was loaded.
+
+    Raises
+    ------
+    ImportError, if it isn't possible to import any requested
+    bindings (either becaues they aren't installed, or because
+    an incompatible library has already been installed)
+    """
+    loaders = {
+               QT_API_PYSIDE2: import_pyside2,
+               QT_API_PYSIDE: import_pyside,
+               QT_API_PYQT: import_pyqt4,
+               QT_API_PYQT5: import_pyqt5,
+               QT_API_PYQTv1: partial(import_pyqt4, version=1),
+               QT_API_PYQT_DEFAULT: partial(import_pyqt4, version=None)
+              }
+
+    for api in api_options:
+
+        if api not in loaders:
+            raise RuntimeError(
+                "Invalid Qt API %r, valid values are: %s" %
+                (api, ", ".join(["%r" % k for k in loaders.keys()])))
+
+        if not can_import(api):
+            continue
+
+        #cannot safely recover from an ImportError during this
+        result = loaders[api]()
+        api = result[-1]  # changed if api = QT_API_PYQT_DEFAULT
+        commit_api(api)
+        return result
+    else:
+        raise ImportError("""
+    Could not load requested Qt binding. Please ensure that
+    PyQt4 >= 4.7, PyQt5, PySide >= 1.0.3 or PySide2 is available,
+    and only one is imported per session.
+
+    Currently-imported Qt library:                              %r
+    PyQt4 available (requires QtCore, QtGui, QtSvg):            %s
+    PyQt5 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
+    PySide >= 1.0.3 installed:                                  %s
+    PySide2 installed:                                          %s
+    Tried to load:                                              %r
+    """ % (loaded_api(),
+           has_binding(QT_API_PYQT),
+           has_binding(QT_API_PYQT5),
+           has_binding(QT_API_PYSIDE),
+           has_binding(QT_API_PYSIDE2),
+           api_options))