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|
"""
Patch recently added ABCs into the standard lib module
``collections.abc`` (Py3) or ``collections`` (Py2).
Usage::
import backports_abc
backports_abc.patch()
or::
try:
from collections.abc import Generator
except ImportError:
from backports_abc import Generator
"""
try:
import collections.abc as _collections_abc
except ImportError:
import collections as _collections_abc
def get_mro(cls):
try:
return cls.__mro__
except AttributeError:
return old_style_mro(cls)
def old_style_mro(cls):
yield cls
for base in cls.__bases__:
for c in old_style_mro(base):
yield c
def mk_gen():
from abc import abstractmethod
required_methods = (
'__iter__', '__next__' if hasattr(iter(()), '__next__') else 'next',
'send', 'throw', 'close')
class Generator(_collections_abc.Iterator):
__slots__ = ()
if '__next__' in required_methods:
def __next__(self):
return self.send(None)
else:
def next(self):
return self.send(None)
@abstractmethod
def send(self, value):
raise StopIteration
@abstractmethod
def throw(self, typ, val=None, tb=None):
if val is None:
if tb is None:
raise typ
val = typ()
if tb is not None:
val = val.with_traceback(tb)
raise val
def close(self):
try:
self.throw(GeneratorExit)
except (GeneratorExit, StopIteration):
pass
else:
raise RuntimeError('generator ignored GeneratorExit')
@classmethod
def __subclasshook__(cls, C):
if cls is Generator:
mro = get_mro(C)
for method in required_methods:
for base in mro:
if method in base.__dict__:
break
else:
return NotImplemented
return True
return NotImplemented
generator = type((lambda: (yield))())
Generator.register(generator)
return Generator
def mk_awaitable():
from abc import abstractmethod, ABCMeta
@abstractmethod
def __await__(self):
yield
@classmethod
def __subclasshook__(cls, C):
if cls is Awaitable:
for B in get_mro(C):
if '__await__' in B.__dict__:
if B.__dict__['__await__']:
return True
break
return NotImplemented
# calling metaclass directly as syntax differs in Py2/Py3
Awaitable = ABCMeta('Awaitable', (), {
'__slots__': (),
'__await__': __await__,
'__subclasshook__': __subclasshook__,
})
return Awaitable
def mk_coroutine():
from abc import abstractmethod
class Coroutine(Awaitable):
__slots__ = ()
@abstractmethod
def send(self, value):
"""Send a value into the coroutine.
Return next yielded value or raise StopIteration.
"""
raise StopIteration
@abstractmethod
def throw(self, typ, val=None, tb=None):
"""Raise an exception in the coroutine.
Return next yielded value or raise StopIteration.
"""
if val is None:
if tb is None:
raise typ
val = typ()
if tb is not None:
val = val.with_traceback(tb)
raise val
def close(self):
"""Raise GeneratorExit inside coroutine.
"""
try:
self.throw(GeneratorExit)
except (GeneratorExit, StopIteration):
pass
else:
raise RuntimeError('coroutine ignored GeneratorExit')
@classmethod
def __subclasshook__(cls, C):
if cls is Coroutine:
mro = get_mro(C)
for method in ('__await__', 'send', 'throw', 'close'):
for base in mro:
if method in base.__dict__:
break
else:
return NotImplemented
return True
return NotImplemented
return Coroutine
###
# make all ABCs available in this module
try:
Generator = _collections_abc.Generator
except AttributeError:
Generator = mk_gen()
try:
Awaitable = _collections_abc.Awaitable
except AttributeError:
Awaitable = mk_awaitable()
try:
Coroutine = _collections_abc.Coroutine
except AttributeError:
Coroutine = mk_coroutine()
try:
from inspect import isawaitable
except ImportError:
def isawaitable(obj):
return isinstance(obj, Awaitable)
###
# allow patching the stdlib
PATCHED = {}
def patch(patch_inspect=True):
"""
Main entry point for patching the ``collections.abc`` and ``inspect``
standard library modules.
"""
PATCHED['collections.abc.Generator'] = _collections_abc.Generator = Generator
PATCHED['collections.abc.Coroutine'] = _collections_abc.Coroutine = Coroutine
PATCHED['collections.abc.Awaitable'] = _collections_abc.Awaitable = Awaitable
if patch_inspect:
import inspect
PATCHED['inspect.isawaitable'] = inspect.isawaitable = isawaitable
|
