Source code for future.standard_library

Python 3 reorganized the standard library (PEP 3108). This module exposes
several standard library modules to Python 2 under their new Python 3

It is designed to be used as follows::

    from future import standard_library

And then these normal Py3 imports work on both Py3 and Py2::

    import builtins
    import copyreg
    import queue
    import reprlib
    import socketserver
    import winreg    # on Windows only
    import html, html.parser, html.entites
    import http, http.client, http.server
    import http.cookies, http.cookiejar
    import urllib.parse, urllib.request, urllib.response, urllib.error, urllib.robotparser
    import xmlrpc.client, xmlrpc.server

    import _thread
    import _dummy_thread
    import _markupbase

    from itertools import filterfalse, zip_longest
    from sys import intern
    from collections import UserDict, UserList, UserString
    from collections import OrderedDict, Counter, ChainMap     # even on Py2.6
    from subprocess import getoutput, getstatusoutput
    from subprocess import check_output              # even on Py2.6

(The renamed modules and functions are still available under their old
names on Python 2.)

This is a cleaner alternative to this idiom (see

        import queue
    except ImportError:
        import Queue as queue

We don't currently support these modules, but would like to::

    import dbm
    import dbm.dumb
    import dbm.gnu
    import  # on Py33
    import pickle     # should (optionally) bring in cPickle on Python 2


from __future__ import absolute_import, division, print_function

import sys
import logging
import imp
import contextlib
import types
import copy
import os

# Make a dedicated logger; leave the root logger to be configured
# by the application.
flog = logging.getLogger('future_stdlib')
_formatter = logging.Formatter(logging.BASIC_FORMAT)
_handler = logging.StreamHandler()

from future.utils import PY2, PY3

# The modules that are defined under the same names on Py3 but with
# different contents in a significant way (e.g. submodules) are:
#   pickle (fast one)
#   dbm
#   urllib
#   test
#   email

REPLACED_MODULES = set(['test', 'urllib', 'pickle', 'dbm'])  # add email and dbm when we support it

# The following module names are not present in Python 2.x, so they cause no
# potential clashes between the old and new names:
#   http
#   html
#   tkinter
#   xmlrpc
# Keys: Py2 / real module names
# Values: Py3 / simulated module names
           # 'cStringIO': 'io',  # there's a new io module in Python 2.6
                                 # that provides StringIO and BytesIO
           # 'StringIO': 'io',   # ditto
           # 'cPickle': 'pickle',
           '__builtin__': 'builtins',
           'copy_reg': 'copyreg',
           'Queue': 'queue',
           'future.moves.socketserver': 'socketserver',
           'ConfigParser': 'configparser',
           'repr': 'reprlib',
           # 'FileDialog': 'tkinter.filedialog',
           # 'tkFileDialog': 'tkinter.filedialog',
           # 'SimpleDialog': 'tkinter.simpledialog',
           # 'tkSimpleDialog': 'tkinter.simpledialog',
           # 'tkColorChooser': 'tkinter.colorchooser',
           # 'tkCommonDialog': 'tkinter.commondialog',
           # 'Dialog': 'tkinter.dialog',
           # 'Tkdnd': 'tkinter.dnd',
           # 'tkFont': 'tkinter.font',
           # 'tkMessageBox': 'tkinter.messagebox',
           # 'ScrolledText': 'tkinter.scrolledtext',
           # 'Tkconstants': 'tkinter.constants',
           # 'Tix': 'tkinter.tix',
           # 'ttk': 'tkinter.ttk',
           # 'Tkinter': 'tkinter',
           '_winreg': 'winreg',
           'thread': '_thread',
           'dummy_thread': '_dummy_thread',
           # 'anydbm': 'dbm',   # causes infinite import loop
           # 'whichdb': 'dbm',  # causes infinite import loop
           # anydbm and whichdb are handled by fix_imports2
           # 'dbhash': 'dbm.bsd',
           # 'dumbdbm': 'dbm.dumb',
           # 'dbm': 'dbm.ndbm',
           # 'gdbm': 'dbm.gnu',
           'future.moves.xmlrpc': 'xmlrpc',
           # '': 'email',    # for use by urllib
           # 'DocXMLRPCServer': 'xmlrpc.server',
           # 'SimpleXMLRPCServer': 'xmlrpc.server',
           # 'httplib': 'http.client',
           # 'htmlentitydefs' : 'html.entities',
           # 'HTMLParser' : 'html.parser',
           # 'Cookie': 'http.cookies',
           # 'cookielib': 'http.cookiejar',
           # 'BaseHTTPServer': 'http.server',
           # 'SimpleHTTPServer': 'http.server',
           # 'CGIHTTPServer': 'http.server',
           # 'future.backports.test': 'test',  # primarily for renaming test_support to support
           # 'commands': 'subprocess',
           # 'urlparse' : 'urllib.parse',
           # 'robotparser' : 'urllib.robotparser',
           # 'abc': '',   # for Py33
           # 'future.utils.six.moves.html': 'html',
           # 'future.utils.six.moves.http': 'http',
           'future.moves.html': 'html',
           'future.moves.http': 'http',
           # 'future.backports.urllib': 'urllib',
           # 'future.utils.six.moves.urllib': 'urllib',
           'future.moves._markupbase': '_markupbase',

# It is complicated and apparently brittle to mess around with the
# ``sys.modules`` cache in order to support "import urllib" meaning two
# different things (Py2.7 urllib and backported Py3.3-like urllib) in different
# contexts. So we require explicit imports for these modules.
assert len(set(RENAMES.values()) & set(REPLACED_MODULES)) == 0

# Harmless renames that we can insert.
# These modules need names from elsewhere being added to them:
#   subprocess: should provide getoutput and other fns from commands
#               module but these fns are missing: getstatus, mk2arg,
#               mkarg
#   re:         needs an ASCII constant that works compatibly with Py3

# etc: see lib2to3/fixes/

# (New module name, new object name, old module name, old object name)
MOVES = [('collections', 'UserList', 'UserList', 'UserList'),
         ('collections', 'UserDict', 'UserDict', 'UserDict'),
         ('collections', 'UserString','UserString', 'UserString'),
         ('collections', 'ChainMap', 'future.backports.misc', 'ChainMap'),
         ('itertools', 'filterfalse','itertools', 'ifilterfalse'),
         ('itertools', 'zip_longest','itertools', 'izip_longest'),
         ('sys', 'intern','__builtin__', 'intern'),
         # The re module has no ASCII flag in Py2, but this is the default.
         # Set re.ASCII to a zero constant. stat.ST_MODE just happens to be one
         # (and it exists on Py2.6+).
         ('re', 'ASCII','stat', 'ST_MODE'),
         ('base64', 'encodebytes','base64', 'encodestring'),
         ('base64', 'decodebytes','base64', 'decodestring'),
         ('subprocess', 'getoutput', 'commands', 'getoutput'),
         ('subprocess', 'getstatusoutput', 'commands', 'getstatusoutput'),
         ('subprocess', 'check_output', 'future.backports.misc', 'check_output'),
         ('math', 'ceil', 'future.backports.misc', 'ceil'),
         ('collections', 'OrderedDict', 'future.backports.misc', 'OrderedDict'),
         ('collections', 'Counter', 'future.backports.misc', 'Counter'),
         ('collections', 'ChainMap', 'future.backports.misc', 'ChainMap'),
         ('itertools', 'count', 'future.backports.misc', 'count'),
         ('reprlib', 'recursive_repr', 'future.backports.misc', 'recursive_repr'),
         ('functools', 'cmp_to_key', 'future.backports.misc', 'cmp_to_key'),

# This is no use, since "import urllib.request" etc. still fails:
#          ('urllib', 'error', 'future.moves.urllib', 'error'),
#          ('urllib', 'parse', 'future.moves.urllib', 'parse'),
#          ('urllib', 'request', 'future.moves.urllib', 'request'),
#          ('urllib', 'response', 'future.moves.urllib', 'response'),
#          ('urllib', 'robotparser', 'future.moves.urllib', 'robotparser'),

# A minimal example of an import hook:
# class WarnOnImport(object):
#     def __init__(self, *args):
#         self.module_names = args
#     def find_module(self, fullname, path=None):
#         if fullname in self.module_names:
#             self.path = path
#             return self
#         return None
#     def load_module(self, name):
#         if name in sys.modules:
#             return sys.modules[name]
#         module_info = imp.find_module(name, self.path)
#         module = imp.load_module(name, *module_info)
#         sys.modules[name] = module
#         flog.warning("Imported deprecated module %s", name)
#         return module

[docs]class RenameImport(object): """ A class for import hooks mapping Py3 module names etc. to the Py2 equivalents. """ # Different RenameImport classes are created when importing this module from # different source files. This causes isinstance(hook, RenameImport) checks # to produce inconsistent results. We add this RENAMER attribute here so # remove_hooks() and install_hooks() can find instances of these classes # easily: RENAMER = True def __init__(self, old_to_new): ''' Pass in a dictionary-like object mapping from old names to new names. E.g. {'ConfigParser': 'configparser', 'cPickle': 'pickle'} ''' self.old_to_new = old_to_new both = set(old_to_new.keys()) & set(old_to_new.values()) assert (len(both) == 0 and len(set(old_to_new.values())) == len(old_to_new.values())), \ 'Ambiguity in renaming (handler not implemented)' self.new_to_old = dict((new, old) for (old, new) in old_to_new.items()) def find_module(self, fullname, path=None): # Handles hierarchical importing: package.module.module2 new_base_names = set([s.split('.')[0] for s in self.new_to_old]) # Before v0.12: Was: if fullname in set(self.old_to_new) | new_base_names: if fullname in new_base_names: return self return None def load_module(self, name): path = None if name in sys.modules: return sys.modules[name] elif name in self.new_to_old: # New name. Look up the corresponding old (Py2) name: oldname = self.new_to_old[name] module = self._find_and_load_module(oldname) # module.__future_module__ = True else: module = self._find_and_load_module(name) # In any case, make it available under the requested (Py3) name sys.modules[name] = module return module def _find_and_load_module(self, name, path=None): """ Finds and loads it. But if there's a . in the name, handles it properly. """ bits = name.split('.') while len(bits) > 1: # Treat the first bit as a package packagename = bits.pop(0) package = self._find_and_load_module(packagename, path) try: path = package.__path__ except AttributeError: # This could be e.g. moves. flog.debug('Package {0} has no __path__.'.format(package)) if name in sys.modules: return sys.modules[name] flog.debug('What to do here?') name = bits[0] module_info = imp.find_module(name, path) return imp.load_module(name, *module_info)
[docs]class hooks(object): """ Acts as a context manager. Saves the state of sys.modules and restores it after the 'with' block. Use like this: >>> from future import standard_library >>> with standard_library.hooks(): ... import http.client >>> import requests For this to work, http.client will be scrubbed from sys.modules after the 'with' block. That way the modules imported in the 'with' block will continue to be accessible in the current namespace but not from any imported modules (like requests). """ 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: if PY2: assert len(set(RENAMES.values()) & set(sys.builtin_module_names)) == 0
[docs]def is_py2_stdlib_module(m): """ Tries to infer whether the module m is from the Python 2 standard library. This may not be reliable on all systems. """ if PY3: return False if not 'stdlib_path' in is_py2_stdlib_module.__dict__: stdlib_files = [contextlib.__file__, os.__file__, copy.__file__] stdlib_paths = [os.path.split(f)[0] for f in stdlib_files] if not len(set(stdlib_paths)) == 1: # This seems to happen on Very strange. We'll try to # ignore it. flog.warn('Multiple locations found for the Python standard ' 'library: %s' % stdlib_paths) # Choose the first one arbitrarily is_py2_stdlib_module.stdlib_path = stdlib_paths[0] if m.__name__ in sys.builtin_module_names: return True if hasattr(m, '__file__'): modpath = os.path.split(m.__file__) if (modpath[0].startswith(is_py2_stdlib_module.stdlib_path) and 'site-packages' not in modpath[0]): return True return False
[docs]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
[docs]def scrub_future_sys_modules(): """ Deprecated. """ return {}
[docs]class suspend_hooks(object): """ Acts as a context manager. Use like this: >>> from future import standard_library >>> standard_library.install_hooks() >>> import http.client >>> # ... >>> with standard_library.suspend_hooks(): >>> import requests # incompatible with ``future``'s standard library hooks If the hooks were disabled before the context, they are not installed when the context is left. """ def __enter__(self): self.hooks_were_installed = detect_hooks() remove_hooks() # self.scrubbed = scrub_future_sys_modules() return self def __exit__(self, *args): if self.hooks_were_installed: install_hooks()
# restore_sys_modules(self.scrubbed)
[docs]def restore_sys_modules(scrubbed): """ Add any previously scrubbed modules back to the sys.modules cache, but only if it's safe to do so. """ clash = set(sys.modules) & set(scrubbed) if len(clash) != 0: # If several, choose one arbitrarily to raise an exception about first = list(clash)[0] raise ImportError('future module {} clashes with Py2 module' .format(first)) sys.modules.update(scrubbed)
[docs]def install_aliases(): """ Monkey-patches the standard library in Py2.6/7 to provide aliases for better Py3 compatibility. """ if PY3: return # if hasattr(install_aliases, 'run_already'): # return for (newmodname, newobjname, oldmodname, oldobjname) in MOVES: __import__(newmodname) # We look up the module in sys.modules because __import__ just returns the # top-level package: newmod = sys.modules[newmodname] # newmod.__future_module__ = True __import__(oldmodname) oldmod = sys.modules[oldmodname] obj = getattr(oldmod, oldobjname) setattr(newmod, newobjname, obj) # Hack for urllib so it appears to have the same structure on Py2 as on Py3 import urllib from future.backports.urllib import request from future.backports.urllib import response from future.backports.urllib import parse from future.backports.urllib import error from future.backports.urllib import robotparser urllib.request = request urllib.response = response urllib.parse = parse urllib.error = error urllib.robotparser = robotparser sys.modules['urllib.request'] = request sys.modules['urllib.response'] = response sys.modules['urllib.parse'] = parse sys.modules['urllib.error'] = error sys.modules['urllib.robotparser'] = robotparser # Patch the test module so it appears to have the same structure on Py2 as on Py3 try: import test except ImportError: pass try: from future.moves.test import support except ImportError: pass else: = support sys.modules[''] = support # Patch the dbm module so it appears to have the same structure on Py2 as on Py3 try: import dbm except ImportError: pass else: from future.moves.dbm import dumb dbm.dumb = dumb sys.modules['dbm.dumb'] = dumb try: from future.moves.dbm import gnu except ImportError: pass else: dbm.gnu = gnu sys.modules['dbm.gnu'] = gnu try: from future.moves.dbm import ndbm except ImportError: pass else: dbm.ndbm = ndbm sys.modules['dbm.ndbm'] = ndbm
# install_aliases.run_already = True
[docs]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))
[docs]def enable_hooks(): """ Deprecated. Use install_hooks() instead. This will be removed by ``future`` v1.0. """ install_hooks()
[docs]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()
[docs]def disable_hooks(): """ Deprecated. Use remove_hooks() instead. This will be removed by ``future`` v1.0. """ remove_hooks()
[docs]def detect_hooks(): """ Returns True if the import hooks are installed, False if not. """ flog.debug('Detecting hooks ...') present = any([hasattr(hook, 'RENAMER') for hook in sys.meta_path]) if present: flog.debug('Detected.') else: flog.debug('Not detected.') return present
# As of v0.12, this no longer happens implicitly: # if not PY3: # install_hooks() if not hasattr(sys, 'py2_modules'): sys.py2_modules = {}
[docs]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
[docs]def import_(module_name, backport=False): """ Pass a (potentially dotted) module name of a Python 3 standard library module. This function imports the module compatibly on Py2 and Py3 and returns the top-level module. Example use: >>> http = import_('http.client') >>> http = import_('http.server') >>> urllib = import_('urllib.request') Then: >>> conn = http.client.HTTPConnection(...) >>> response = urllib.request.urlopen('') >>> # etc. Use as follows: >>> package_name = import_(module_name) On Py3, equivalent to this: >>> import module_name On Py2, equivalent to this if backport=False: >>> from future.moves import module_name or to this if backport=True: >>> from future.backports import module_name except that it also handles dotted module names such as ``http.client`` The effect then is like this: >>> from future.backports import module >>> from future.backports.module import submodule >>> module.submodule = submodule Note that this would be a SyntaxError in Python: >>> from future.backports import http.client """ # Python 2.6 doesn't have importlib in the stdlib, so it requires # the backported ``importlib`` package from PyPI as a dependency to use # this function: import importlib if PY3: return __import__(module_name) else: # client.blah = blah # Then http.client = client # etc. if backport: prefix = 'future.backports' else: prefix = 'future.moves' parts = prefix.split('.') + module_name.split('.') modules = [] for i, part in enumerate(parts): sofar = '.'.join(parts[:i+1]) modules.append(importlib.import_module(sofar)) for i, part in reversed(list(enumerate(parts))): if i == 0: break setattr(modules[i-1], part, modules[i]) # Return the next-most top-level module after future.backports / future.moves: return modules[2]
[docs]def from_import(module_name, *symbol_names, **kwargs): """ Example use: >>> HTTPConnection = from_import('http.client', 'HTTPConnection') >>> HTTPServer = from_import('http.server', 'HTTPServer') >>> urlopen, urlparse = from_import('urllib.request', 'urlopen', 'urlparse') Equivalent to this on Py3: >>> from module_name import symbol_names[0], symbol_names[1], ... and this on Py2: >>> from future.moves.module_name import symbol_names[0], ... or: >>> from future.backports.module_name import symbol_names[0], ... except that it also handles dotted module names such as ``http.client``. """ if PY3: return __import__(module_name) else: if 'backport' in kwargs and bool(kwargs['backport']): prefix = 'future.backports' else: prefix = 'future.moves' parts = prefix.split('.') + module_name.split('.') module = importlib.import_module(prefix + '.' + module_name) output = [getattr(module, name) for name in symbol_names] if len(output) == 1: return output[0] else: return output
[docs]class exclude_local_folder_imports(object): """ A context-manager that prevents standard library modules like configparser from being imported from the local python-future source folder on Py3. (This was need prior to v0.16.0 because the presence of a configparser folder would otherwise have prevented setuptools from running on Py3. Maybe it's not needed any more?) """ def __init__(self, *args): assert len(args) > 0 self.module_names = args # Disallow dotted module names like http.client: if any(['.' in m for m in self.module_names]): raise NotImplementedError('Dotted module names are not supported') def __enter__(self): self.old_sys_path = copy.copy(sys.path) self.old_sys_modules = copy.copy(sys.modules) if sys.version_info[0] < 3: return # The presence of all these indicates we've found our source folder, # because `builtins` won't have been installed in site-packages by FUTURE_SOURCE_SUBFOLDERS = ['future', 'past', 'libfuturize', 'libpasteurize', 'builtins'] # Look for the future source folder: for folder in self.old_sys_path: if all([os.path.exists(os.path.join(folder, subfolder)) for subfolder in FUTURE_SOURCE_SUBFOLDERS]): # Found it. Remove it. sys.path.remove(folder) # Ensure we import the system module: for m in self.module_names: # Delete the module and any submodules from sys.modules: # for key in list(sys.modules): # if key == m or key.startswith(m + '.'): # try: # del sys.modules[key] # except KeyError: # pass try: module = __import__(m, level=0) except ImportError: # There's a problem importing the system module. E.g. the # winreg module is not available except on Windows. pass def __exit__(self, *args): # Restore sys.path and sys.modules: sys.path = self.old_sys_path for m in set(self.old_sys_modules.keys()) - set(sys.modules.keys()): sys.modules[m] = self.old_sys_modules[m]
TOP_LEVEL_MODULES = ['builtins', 'copyreg', 'html', 'http', 'queue', 'reprlib', 'socketserver', 'test', 'tkinter', 'winreg', 'xmlrpc', '_dummy_thread', '_markupbase', '_thread', ] def import_top_level_modules(): with exclude_local_folder_imports(*TOP_LEVEL_MODULES): for m in TOP_LEVEL_MODULES: try: __import__(m) except ImportError: # e.g. winreg pass