python类hooks()的实例源码

def scrub_py2_sys_modules():
    """
    Removes any Python 2 standard library modules from ``sys.modules`` that
    would interfere with Py3-style imports using import hooks. Examples are
    modules with the same names (like urllib or email).

    (Note that currently import hooks are disabled for modules like these
    with ambiguous names anyway ...)
    """
    if PY3:
        return {}
    scrubbed = {}
    for modulename in REPLACED_MODULES & set(RENAMES.keys()):
        if not modulename in sys.modules:
            continue

        module = sys.modules[modulename]

        if is_py2_stdlib_module(module):
            flog.debug('Deleting (Py2) {} from sys.modules'.format(modulename))
            scrubbed[modulename] = sys.modules[modulename]
            del sys.modules[modulename]
    return scrubbed

def install_hooks():
    """
    This function installs the future.standard_library import hook into
    sys.meta_path.
    """
    if PY3:
        return

    install_aliases()

    flog.debug('sys.meta_path was: {0}'.format(sys.meta_path))
    flog.debug('Installing hooks ...')

    # Add it unless it's there already
    newhook = RenameImport(RENAMES)
    if not detect_hooks():
        sys.meta_path.append(newhook)
    flog.debug('sys.meta_path is now: {0}'.format(sys.meta_path))

def remove_hooks(scrub_sys_modules=False):
    """
    This function removes the import hook from sys.meta_path.
    """
    if PY3:
        return
    flog.debug('Uninstalling hooks ...')
    # Loop backwards, so deleting items keeps the ordering:
    for i, hook in list(enumerate(sys.meta_path))[::-1]:
        if hasattr(hook, 'RENAMER'):
            del sys.meta_path[i]

    # Explicit is better than implicit. In the future the interface should
    # probably change so that scrubbing the import hooks requires a separate
    # function call. Left as is for now for backward compatibility with
    # v0.11.x.
    if scrub_sys_modules:
        scrub_future_sys_modules()

def scrub_py2_sys_modules():
    """
    Removes any Python 2 standard library modules from ``sys.modules`` that
    would interfere with Py3-style imports using import hooks. Examples are
    modules with the same names (like urllib or email).

    (Note that currently import hooks are disabled for modules like these
    with ambiguous names anyway ...)
    """
    if PY3:
        return {}
    scrubbed = {}
    for modulename in REPLACED_MODULES & set(RENAMES.keys()):
        if not modulename in sys.modules:
            continue

        module = sys.modules[modulename]

        if is_py2_stdlib_module(module):
            flog.debug('Deleting (Py2) {} from sys.modules'.format(modulename))
            scrubbed[modulename] = sys.modules[modulename]
            del sys.modules[modulename]
    return scrubbed

def install_hooks():
    """
    This function installs the future.standard_library import hook into
    sys.meta_path.
    """
    if PY3:
        return

    install_aliases()

    flog.debug('sys.meta_path was: {0}'.format(sys.meta_path))
    flog.debug('Installing hooks ...')

    # Add it unless it's there already
    newhook = RenameImport(RENAMES)
    if not detect_hooks():
        sys.meta_path.append(newhook)
    flog.debug('sys.meta_path is now: {0}'.format(sys.meta_path))

def remove_hooks(scrub_sys_modules=False):
    """
    This function removes the import hook from sys.meta_path.
    """
    if PY3:
        return
    flog.debug('Uninstalling hooks ...')
    # Loop backwards, so deleting items keeps the ordering:
    for i, hook in list(enumerate(sys.meta_path))[::-1]:
        if hasattr(hook, 'RENAMER'):
            del sys.meta_path[i]

    # Explicit is better than implicit. In the future the interface should
    # probably change so that scrubbing the import hooks requires a separate
    # function call. Left as is for now for backward compatibility with
    # v0.11.x.
    if scrub_sys_modules:
        scrub_future_sys_modules()

def __enter__(self):
        # flog.debug('Entering hooks context manager')
        self.old_sys_modules = copy.copy(sys.modules)
        self.hooks_were_installed = detect_hooks()
        # self.scrubbed = scrub_py2_sys_modules()
        install_hooks()
        return self

def __exit__(self, *args):
        # flog.debug('Exiting hooks context manager')
        # restore_sys_modules(self.scrubbed)
        if not self.hooks_were_installed:
            remove_hooks()
        # scrub_future_sys_modules()

# Sanity check for is_py2_stdlib_module(): We aren't replacing any
# builtin modules names:

def cache_py2_modules():
    """
    Currently this function is unneeded, as we are not attempting to provide import hooks
    for modules with ambiguous names: email, urllib, pickle.
    """
    if len(sys.py2_modules) != 0:
        return
    assert not detect_hooks()
    import urllib
    sys.py2_modules['urllib'] = urllib

    import email
    sys.py2_modules['email'] = email

    import pickle
    sys.py2_modules['pickle'] = pickle

    # Not all Python installations have test module. (Anaconda doesn't, for example.)
    # try:
    #     import test
    # except ImportError:
    #     sys.py2_modules['test'] = None
    # sys.py2_modules['test'] = test

    # import dbm
    # sys.py2_modules['dbm'] = dbm

def test_urllib(self):
        """
        Tests that urllib isn't changed from under our feet. (This might not
        even be a problem?)
        """
        from future import standard_library
        import urllib
        orig_file = urllib.__file__
        with standard_library.hooks():
            import urllib.response
        self.assertEqual(orig_file, urllib.__file__)

def test_urllib_imports_cm(self):
        with standard_library.hooks():
            import urllib
            import urllib.parse
            import urllib.request
            import urllib.robotparser
            import urllib.error
            import urllib.response
        self.assertTrue(True)

def __enter__(self):
        # flog.debug('Entering hooks context manager')
        self.old_sys_modules = copy.copy(sys.modules)
        self.hooks_were_installed = detect_hooks()
        # self.scrubbed = scrub_py2_sys_modules()
        install_hooks()
        return self

def cache_py2_modules():
    """
    Currently this function is unneeded, as we are not attempting to provide import hooks
    for modules with ambiguous names: email, urllib, pickle.
    """
    if len(sys.py2_modules) != 0:
        return
    assert not detect_hooks()
    import urllib
    sys.py2_modules['urllib'] = urllib

    import email
    sys.py2_modules['email'] = email

    import pickle
    sys.py2_modules['pickle'] = pickle

    # Not all Python installations have test module. (Anaconda doesn't, for example.)
    # try:
    #     import test
    # except ImportError:
    #     sys.py2_modules['test'] = None
    # sys.py2_modules['test'] = test

    # import dbm
    # sys.py2_modules['dbm'] = dbm

def __enter__(self):
        # flog.debug('Entering hooks context manager')
        self.old_sys_modules = copy.copy(sys.modules)
        self.hooks_were_installed = detect_hooks()
        # self.scrubbed = scrub_py2_sys_modules()
        install_hooks()
        return self

def __exit__(self, *args):
        # flog.debug('Exiting hooks context manager')
        # restore_sys_modules(self.scrubbed)
        if not self.hooks_were_installed:
            remove_hooks()
        # scrub_future_sys_modules()

# Sanity check for is_py2_stdlib_module(): We aren't replacing any
# builtin modules names:

def cache_py2_modules():
    """
    Currently this function is unneeded, as we are not attempting to provide import hooks
    for modules with ambiguous names: email, urllib, pickle.
    """
    if len(sys.py2_modules) != 0:
        return
    assert not detect_hooks()
    import urllib
    sys.py2_modules['urllib'] = urllib

    import email
    sys.py2_modules['email'] = email

    import pickle
    sys.py2_modules['pickle'] = pickle

    # Not all Python installations have test module. (Anaconda doesn't, for example.)
    # try:
    #     import test
    # except ImportError:
    #     sys.py2_modules['test'] = None
    # sys.py2_modules['test'] = test

    # import dbm
    # sys.py2_modules['dbm'] = dbm

def __enter__(self):
        # flog.debug('Entering hooks context manager')
        self.old_sys_modules = copy.copy(sys.modules)
        self.hooks_were_installed = detect_hooks()
        # self.scrubbed = scrub_py2_sys_modules()
        install_hooks()
        return self

def __exit__(self, *args):
        # flog.debug('Exiting hooks context manager')
        # restore_sys_modules(self.scrubbed)
        if not self.hooks_were_installed:
            remove_hooks()
        # scrub_future_sys_modules()

# Sanity check for is_py2_stdlib_module(): We aren't replacing any
# builtin modules names:

def cache_py2_modules():
    """
    Currently this function is unneeded, as we are not attempting to provide import hooks
    for modules with ambiguous names: email, urllib, pickle.
    """
    if len(sys.py2_modules) != 0:
        return
    assert not detect_hooks()
    import urllib
    sys.py2_modules['urllib'] = urllib

    import email
    sys.py2_modules['email'] = email

    import pickle
    sys.py2_modules['pickle'] = pickle

    # Not all Python installations have test module. (Anaconda doesn't, for example.)
    # try:
    #     import test
    # except ImportError:
    #     sys.py2_modules['test'] = None
    # sys.py2_modules['test'] = test

    # import dbm
    # sys.py2_modules['dbm'] = dbm

def __enter__(self):
        # flog.debug('Entering hooks context manager')
        self.old_sys_modules = copy.copy(sys.modules)
        self.hooks_were_installed = detect_hooks()
        # self.scrubbed = scrub_py2_sys_modules()
        install_hooks()
        return self