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742 lines
20 KiB
742 lines
20 KiB
5 years ago
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"""
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A selection of cross-compatible functions for Python 2 and 3.
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This module exports useful functions for 2/3 compatible code:
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* bind_method: binds functions to classes
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* ``native_str_to_bytes`` and ``bytes_to_native_str``
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* ``native_str``: always equal to the native platform string object (because
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this may be shadowed by imports from future.builtins)
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* lists: lrange(), lmap(), lzip(), lfilter()
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* iterable method compatibility:
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- iteritems, iterkeys, itervalues
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- viewitems, viewkeys, viewvalues
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These use the original method if available, otherwise they use items,
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keys, values.
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* types:
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* text_type: unicode in Python 2, str in Python 3
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* binary_type: str in Python 2, bytes in Python 3
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* string_types: basestring in Python 2, str in Python 3
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* bchr(c):
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Take an integer and make a 1-character byte string
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* bord(c)
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Take the result of indexing on a byte string and make an integer
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* tobytes(s)
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Take a text string, a byte string, or a sequence of characters taken
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from a byte string, and make a byte string.
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* raise_from()
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* raise_with_traceback()
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This module also defines these decorators:
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* ``python_2_unicode_compatible``
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* ``with_metaclass``
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* ``implements_iterator``
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Some of the functions in this module come from the following sources:
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* Jinja2 (BSD licensed: see
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https://github.com/mitsuhiko/jinja2/blob/master/LICENSE)
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* Pandas compatibility module pandas.compat
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* six.py by Benjamin Peterson
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* Django
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"""
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import types
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import sys
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import numbers
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import functools
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import copy
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import inspect
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PY3 = sys.version_info[0] == 3
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PY35_PLUS = sys.version_info[0:2] >= (3, 5)
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PY36_PLUS = sys.version_info[0:2] >= (3, 6)
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PY2 = sys.version_info[0] == 2
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PY26 = sys.version_info[0:2] == (2, 6)
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PY27 = sys.version_info[0:2] == (2, 7)
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PYPY = hasattr(sys, 'pypy_translation_info')
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def python_2_unicode_compatible(cls):
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"""
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A decorator that defines __unicode__ and __str__ methods under Python
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2. Under Python 3, this decorator is a no-op.
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To support Python 2 and 3 with a single code base, define a __str__
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method returning unicode text and apply this decorator to the class, like
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this::
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>>> from future.utils import python_2_unicode_compatible
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>>> @python_2_unicode_compatible
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... class MyClass(object):
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... def __str__(self):
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... return u'Unicode string: \u5b54\u5b50'
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>>> a = MyClass()
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Then, after this import:
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>>> from future.builtins import str
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the following is ``True`` on both Python 3 and 2::
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>>> str(a) == a.encode('utf-8').decode('utf-8')
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True
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and, on a Unicode-enabled terminal with the right fonts, these both print the
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Chinese characters for Confucius::
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>>> print(a)
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>>> print(str(a))
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The implementation comes from django.utils.encoding.
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"""
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if not PY3:
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cls.__unicode__ = cls.__str__
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cls.__str__ = lambda self: self.__unicode__().encode('utf-8')
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return cls
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def with_metaclass(meta, *bases):
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"""
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Function from jinja2/_compat.py. License: BSD.
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Use it like this::
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class BaseForm(object):
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pass
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class FormType(type):
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pass
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class Form(with_metaclass(FormType, BaseForm)):
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pass
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This requires a bit of explanation: the basic idea is to make a
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dummy metaclass for one level of class instantiation that replaces
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itself with the actual metaclass. Because of internal type checks
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we also need to make sure that we downgrade the custom metaclass
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for one level to something closer to type (that's why __call__ and
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__init__ comes back from type etc.).
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This has the advantage over six.with_metaclass of not introducing
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dummy classes into the final MRO.
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"""
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class metaclass(meta):
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__call__ = type.__call__
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__init__ = type.__init__
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def __new__(cls, name, this_bases, d):
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if this_bases is None:
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return type.__new__(cls, name, (), d)
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return meta(name, bases, d)
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return metaclass('temporary_class', None, {})
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# Definitions from pandas.compat and six.py follow:
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if PY3:
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def bchr(s):
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return bytes([s])
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def bstr(s):
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if isinstance(s, str):
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return bytes(s, 'latin-1')
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else:
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return bytes(s)
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def bord(s):
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return s
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string_types = str,
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integer_types = int,
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class_types = type,
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text_type = str
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binary_type = bytes
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else:
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# Python 2
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def bchr(s):
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return chr(s)
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def bstr(s):
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return str(s)
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def bord(s):
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return ord(s)
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string_types = basestring,
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integer_types = (int, long)
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class_types = (type, types.ClassType)
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text_type = unicode
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binary_type = str
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###
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if PY3:
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def tobytes(s):
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if isinstance(s, bytes):
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return s
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else:
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if isinstance(s, str):
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return s.encode('latin-1')
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else:
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return bytes(s)
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else:
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# Python 2
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def tobytes(s):
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if isinstance(s, unicode):
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return s.encode('latin-1')
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else:
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return ''.join(s)
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tobytes.__doc__ = """
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Encodes to latin-1 (where the first 256 chars are the same as
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ASCII.)
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"""
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if PY3:
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def native_str_to_bytes(s, encoding='utf-8'):
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return s.encode(encoding)
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def bytes_to_native_str(b, encoding='utf-8'):
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return b.decode(encoding)
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def text_to_native_str(t, encoding=None):
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return t
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else:
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# Python 2
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def native_str_to_bytes(s, encoding=None):
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from future.types import newbytes # to avoid a circular import
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return newbytes(s)
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def bytes_to_native_str(b, encoding=None):
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return native(b)
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def text_to_native_str(t, encoding='ascii'):
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"""
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Use this to create a Py2 native string when "from __future__ import
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unicode_literals" is in effect.
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"""
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return unicode(t).encode(encoding)
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native_str_to_bytes.__doc__ = """
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On Py3, returns an encoded string.
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On Py2, returns a newbytes type, ignoring the ``encoding`` argument.
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"""
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if PY3:
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# list-producing versions of the major Python iterating functions
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def lrange(*args, **kwargs):
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return list(range(*args, **kwargs))
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def lzip(*args, **kwargs):
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return list(zip(*args, **kwargs))
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def lmap(*args, **kwargs):
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return list(map(*args, **kwargs))
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def lfilter(*args, **kwargs):
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return list(filter(*args, **kwargs))
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else:
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import __builtin__
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# Python 2-builtin ranges produce lists
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lrange = __builtin__.range
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lzip = __builtin__.zip
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lmap = __builtin__.map
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lfilter = __builtin__.filter
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def isidentifier(s, dotted=False):
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'''
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|
A function equivalent to the str.isidentifier method on Py3
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'''
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if dotted:
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return all(isidentifier(a) for a in s.split('.'))
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if PY3:
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return s.isidentifier()
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else:
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import re
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|
_name_re = re.compile(r"[a-zA-Z_][a-zA-Z0-9_]*$")
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return bool(_name_re.match(s))
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def viewitems(obj, **kwargs):
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"""
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Function for iterating over dictionary items with the same set-like
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behaviour on Py2.7 as on Py3.
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Passes kwargs to method."""
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func = getattr(obj, "viewitems", None)
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if not func:
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func = obj.items
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return func(**kwargs)
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|
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|
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def viewkeys(obj, **kwargs):
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"""
|
||
|
Function for iterating over dictionary keys with the same set-like
|
||
|
behaviour on Py2.7 as on Py3.
|
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|
|
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|
Passes kwargs to method."""
|
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func = getattr(obj, "viewkeys", None)
|
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|
if not func:
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|
func = obj.keys
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return func(**kwargs)
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||
|
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||
|
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|
def viewvalues(obj, **kwargs):
|
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|
"""
|
||
|
Function for iterating over dictionary values with the same set-like
|
||
|
behaviour on Py2.7 as on Py3.
|
||
|
|
||
|
Passes kwargs to method."""
|
||
|
func = getattr(obj, "viewvalues", None)
|
||
|
if not func:
|
||
|
func = obj.values
|
||
|
return func(**kwargs)
|
||
|
|
||
|
|
||
|
def iteritems(obj, **kwargs):
|
||
|
"""Use this only if compatibility with Python versions before 2.7 is
|
||
|
required. Otherwise, prefer viewitems().
|
||
|
"""
|
||
|
func = getattr(obj, "iteritems", None)
|
||
|
if not func:
|
||
|
func = obj.items
|
||
|
return func(**kwargs)
|
||
|
|
||
|
|
||
|
def iterkeys(obj, **kwargs):
|
||
|
"""Use this only if compatibility with Python versions before 2.7 is
|
||
|
required. Otherwise, prefer viewkeys().
|
||
|
"""
|
||
|
func = getattr(obj, "iterkeys", None)
|
||
|
if not func:
|
||
|
func = obj.keys
|
||
|
return func(**kwargs)
|
||
|
|
||
|
|
||
|
def itervalues(obj, **kwargs):
|
||
|
"""Use this only if compatibility with Python versions before 2.7 is
|
||
|
required. Otherwise, prefer viewvalues().
|
||
|
"""
|
||
|
func = getattr(obj, "itervalues", None)
|
||
|
if not func:
|
||
|
func = obj.values
|
||
|
return func(**kwargs)
|
||
|
|
||
|
|
||
|
def bind_method(cls, name, func):
|
||
|
"""Bind a method to class, python 2 and python 3 compatible.
|
||
|
|
||
|
Parameters
|
||
|
----------
|
||
|
|
||
|
cls : type
|
||
|
class to receive bound method
|
||
|
name : basestring
|
||
|
name of method on class instance
|
||
|
func : function
|
||
|
function to be bound as method
|
||
|
|
||
|
Returns
|
||
|
-------
|
||
|
None
|
||
|
"""
|
||
|
# only python 2 has an issue with bound/unbound methods
|
||
|
if not PY3:
|
||
|
setattr(cls, name, types.MethodType(func, None, cls))
|
||
|
else:
|
||
|
setattr(cls, name, func)
|
||
|
|
||
|
|
||
|
def getexception():
|
||
|
return sys.exc_info()[1]
|
||
|
|
||
|
|
||
|
def _get_caller_globals_and_locals():
|
||
|
"""
|
||
|
Returns the globals and locals of the calling frame.
|
||
|
|
||
|
Is there an alternative to frame hacking here?
|
||
|
"""
|
||
|
caller_frame = inspect.stack()[2]
|
||
|
myglobals = caller_frame[0].f_globals
|
||
|
mylocals = caller_frame[0].f_locals
|
||
|
return myglobals, mylocals
|
||
|
|
||
|
|
||
|
def _repr_strip(mystring):
|
||
|
"""
|
||
|
Returns the string without any initial or final quotes.
|
||
|
"""
|
||
|
r = repr(mystring)
|
||
|
if r.startswith("'") and r.endswith("'"):
|
||
|
return r[1:-1]
|
||
|
else:
|
||
|
return r
|
||
|
|
||
|
|
||
|
if PY3:
|
||
|
def raise_from(exc, cause):
|
||
|
"""
|
||
|
Equivalent to:
|
||
|
|
||
|
raise EXCEPTION from CAUSE
|
||
|
|
||
|
on Python 3. (See PEP 3134).
|
||
|
"""
|
||
|
myglobals, mylocals = _get_caller_globals_and_locals()
|
||
|
|
||
|
# We pass the exception and cause along with other globals
|
||
|
# when we exec():
|
||
|
myglobals = myglobals.copy()
|
||
|
myglobals['__python_future_raise_from_exc'] = exc
|
||
|
myglobals['__python_future_raise_from_cause'] = cause
|
||
|
execstr = "raise __python_future_raise_from_exc from __python_future_raise_from_cause"
|
||
|
exec(execstr, myglobals, mylocals)
|
||
|
|
||
|
def raise_(tp, value=None, tb=None):
|
||
|
"""
|
||
|
A function that matches the Python 2.x ``raise`` statement. This
|
||
|
allows re-raising exceptions with the cls value and traceback on
|
||
|
Python 2 and 3.
|
||
|
"""
|
||
|
if value is not None and isinstance(tp, Exception):
|
||
|
raise TypeError("instance exception may not have a separate value")
|
||
|
if value is not None:
|
||
|
exc = tp(value)
|
||
|
else:
|
||
|
exc = tp
|
||
|
if exc.__traceback__ is not tb:
|
||
|
raise exc.with_traceback(tb)
|
||
|
raise exc
|
||
|
|
||
|
def raise_with_traceback(exc, traceback=Ellipsis):
|
||
|
if traceback == Ellipsis:
|
||
|
_, _, traceback = sys.exc_info()
|
||
|
raise exc.with_traceback(traceback)
|
||
|
|
||
|
else:
|
||
|
def raise_from(exc, cause):
|
||
|
"""
|
||
|
Equivalent to:
|
||
|
|
||
|
raise EXCEPTION from CAUSE
|
||
|
|
||
|
on Python 3. (See PEP 3134).
|
||
|
"""
|
||
|
# Is either arg an exception class (e.g. IndexError) rather than
|
||
|
# instance (e.g. IndexError('my message here')? If so, pass the
|
||
|
# name of the class undisturbed through to "raise ... from ...".
|
||
|
if isinstance(exc, type) and issubclass(exc, Exception):
|
||
|
e = exc()
|
||
|
# exc = exc.__name__
|
||
|
# execstr = "e = " + _repr_strip(exc) + "()"
|
||
|
# myglobals, mylocals = _get_caller_globals_and_locals()
|
||
|
# exec(execstr, myglobals, mylocals)
|
||
|
else:
|
||
|
e = exc
|
||
|
e.__suppress_context__ = False
|
||
|
if isinstance(cause, type) and issubclass(cause, Exception):
|
||
|
e.__cause__ = cause()
|
||
|
e.__suppress_context__ = True
|
||
|
elif cause is None:
|
||
|
e.__cause__ = None
|
||
|
e.__suppress_context__ = True
|
||
|
elif isinstance(cause, BaseException):
|
||
|
e.__cause__ = cause
|
||
|
e.__suppress_context__ = True
|
||
|
else:
|
||
|
raise TypeError("exception causes must derive from BaseException")
|
||
|
e.__context__ = sys.exc_info()[1]
|
||
|
raise e
|
||
|
|
||
|
exec('''
|
||
|
def raise_(tp, value=None, tb=None):
|
||
|
raise tp, value, tb
|
||
|
|
||
|
def raise_with_traceback(exc, traceback=Ellipsis):
|
||
|
if traceback == Ellipsis:
|
||
|
_, _, traceback = sys.exc_info()
|
||
|
raise exc, None, traceback
|
||
|
'''.strip())
|
||
|
|
||
|
|
||
|
raise_with_traceback.__doc__ = (
|
||
|
"""Raise exception with existing traceback.
|
||
|
If traceback is not passed, uses sys.exc_info() to get traceback."""
|
||
|
)
|
||
|
|
||
|
|
||
|
# Deprecated alias for backward compatibility with ``future`` versions < 0.11:
|
||
|
reraise = raise_
|
||
|
|
||
|
|
||
|
def implements_iterator(cls):
|
||
|
'''
|
||
|
From jinja2/_compat.py. License: BSD.
|
||
|
|
||
|
Use as a decorator like this::
|
||
|
|
||
|
@implements_iterator
|
||
|
class UppercasingIterator(object):
|
||
|
def __init__(self, iterable):
|
||
|
self._iter = iter(iterable)
|
||
|
def __iter__(self):
|
||
|
return self
|
||
|
def __next__(self):
|
||
|
return next(self._iter).upper()
|
||
|
|
||
|
'''
|
||
|
if PY3:
|
||
|
return cls
|
||
|
else:
|
||
|
cls.next = cls.__next__
|
||
|
del cls.__next__
|
||
|
return cls
|
||
|
|
||
|
if PY3:
|
||
|
get_next = lambda x: x.next
|
||
|
else:
|
||
|
get_next = lambda x: x.__next__
|
||
|
|
||
|
|
||
|
def encode_filename(filename):
|
||
|
if PY3:
|
||
|
return filename
|
||
|
else:
|
||
|
if isinstance(filename, unicode):
|
||
|
return filename.encode('utf-8')
|
||
|
return filename
|
||
|
|
||
|
|
||
|
def is_new_style(cls):
|
||
|
"""
|
||
|
Python 2.7 has both new-style and old-style classes. Old-style classes can
|
||
|
be pesky in some circumstances, such as when using inheritance. Use this
|
||
|
function to test for whether a class is new-style. (Python 3 only has
|
||
|
new-style classes.)
|
||
|
"""
|
||
|
return hasattr(cls, '__class__') and ('__dict__' in dir(cls)
|
||
|
or hasattr(cls, '__slots__'))
|
||
|
|
||
|
# The native platform string and bytes types. Useful because ``str`` and
|
||
|
# ``bytes`` are redefined on Py2 by ``from future.builtins import *``.
|
||
|
native_str = str
|
||
|
native_bytes = bytes
|
||
|
|
||
|
|
||
|
def istext(obj):
|
||
|
"""
|
||
|
Deprecated. Use::
|
||
|
>>> isinstance(obj, str)
|
||
|
after this import:
|
||
|
>>> from future.builtins import str
|
||
|
"""
|
||
|
return isinstance(obj, type(u''))
|
||
|
|
||
|
|
||
|
def isbytes(obj):
|
||
|
"""
|
||
|
Deprecated. Use::
|
||
|
>>> isinstance(obj, bytes)
|
||
|
after this import:
|
||
|
>>> from future.builtins import bytes
|
||
|
"""
|
||
|
return isinstance(obj, type(b''))
|
||
|
|
||
|
|
||
|
def isnewbytes(obj):
|
||
|
"""
|
||
|
Equivalent to the result of ``isinstance(obj, newbytes)`` were
|
||
|
``__instancecheck__`` not overridden on the newbytes subclass. In
|
||
|
other words, it is REALLY a newbytes instance, not a Py2 native str
|
||
|
object?
|
||
|
"""
|
||
|
# TODO: generalize this so that it works with subclasses of newbytes
|
||
|
# Import is here to avoid circular imports:
|
||
|
from future.types.newbytes import newbytes
|
||
|
return type(obj) == newbytes
|
||
|
|
||
|
|
||
|
def isint(obj):
|
||
|
"""
|
||
|
Deprecated. Tests whether an object is a Py3 ``int`` or either a Py2 ``int`` or
|
||
|
``long``.
|
||
|
|
||
|
Instead of using this function, you can use:
|
||
|
|
||
|
>>> from future.builtins import int
|
||
|
>>> isinstance(obj, int)
|
||
|
|
||
|
The following idiom is equivalent:
|
||
|
|
||
|
>>> from numbers import Integral
|
||
|
>>> isinstance(obj, Integral)
|
||
|
"""
|
||
|
|
||
|
return isinstance(obj, numbers.Integral)
|
||
|
|
||
|
|
||
|
def native(obj):
|
||
|
"""
|
||
|
On Py3, this is a no-op: native(obj) -> obj
|
||
|
|
||
|
On Py2, returns the corresponding native Py2 types that are
|
||
|
superclasses for backported objects from Py3:
|
||
|
|
||
|
>>> from builtins import str, bytes, int
|
||
|
|
||
|
>>> native(str(u'ABC'))
|
||
|
u'ABC'
|
||
|
>>> type(native(str(u'ABC')))
|
||
|
unicode
|
||
|
|
||
|
>>> native(bytes(b'ABC'))
|
||
|
b'ABC'
|
||
|
>>> type(native(bytes(b'ABC')))
|
||
|
bytes
|
||
|
|
||
|
>>> native(int(10**20))
|
||
|
100000000000000000000L
|
||
|
>>> type(native(int(10**20)))
|
||
|
long
|
||
|
|
||
|
Existing native types on Py2 will be returned unchanged:
|
||
|
|
||
|
>>> type(native(u'ABC'))
|
||
|
unicode
|
||
|
"""
|
||
|
if hasattr(obj, '__native__'):
|
||
|
return obj.__native__()
|
||
|
else:
|
||
|
return obj
|
||
|
|
||
|
|
||
|
# Implementation of exec_ is from ``six``:
|
||
|
if PY3:
|
||
|
import builtins
|
||
|
exec_ = getattr(builtins, "exec")
|
||
|
else:
|
||
|
def exec_(code, globs=None, locs=None):
|
||
|
"""Execute code in a namespace."""
|
||
|
if globs is None:
|
||
|
frame = sys._getframe(1)
|
||
|
globs = frame.f_globals
|
||
|
if locs is None:
|
||
|
locs = frame.f_locals
|
||
|
del frame
|
||
|
elif locs is None:
|
||
|
locs = globs
|
||
|
exec("""exec code in globs, locs""")
|
||
|
|
||
|
|
||
|
# Defined here for backward compatibility:
|
||
|
def old_div(a, b):
|
||
|
"""
|
||
|
DEPRECATED: import ``old_div`` from ``past.utils`` instead.
|
||
|
|
||
|
Equivalent to ``a / b`` on Python 2 without ``from __future__ import
|
||
|
division``.
|
||
|
|
||
|
TODO: generalize this to other objects (like arrays etc.)
|
||
|
"""
|
||
|
if isinstance(a, numbers.Integral) and isinstance(b, numbers.Integral):
|
||
|
return a // b
|
||
|
else:
|
||
|
return a / b
|
||
|
|
||
|
|
||
|
def as_native_str(encoding='utf-8'):
|
||
|
'''
|
||
|
A decorator to turn a function or method call that returns text, i.e.
|
||
|
unicode, into one that returns a native platform str.
|
||
|
|
||
|
Use it as a decorator like this::
|
||
|
|
||
|
from __future__ import unicode_literals
|
||
|
|
||
|
class MyClass(object):
|
||
|
@as_native_str(encoding='ascii')
|
||
|
def __repr__(self):
|
||
|
return next(self._iter).upper()
|
||
|
'''
|
||
|
if PY3:
|
||
|
return lambda f: f
|
||
|
else:
|
||
|
def encoder(f):
|
||
|
@functools.wraps(f)
|
||
|
def wrapper(*args, **kwargs):
|
||
|
return f(*args, **kwargs).encode(encoding=encoding)
|
||
|
return wrapper
|
||
|
return encoder
|
||
|
|
||
|
# listvalues and listitems definitions from Nick Coghlan's (withdrawn)
|
||
|
# PEP 496:
|
||
|
try:
|
||
|
dict.iteritems
|
||
|
except AttributeError:
|
||
|
# Python 3
|
||
|
def listvalues(d):
|
||
|
return list(d.values())
|
||
|
def listitems(d):
|
||
|
return list(d.items())
|
||
|
else:
|
||
|
# Python 2
|
||
|
def listvalues(d):
|
||
|
return d.values()
|
||
|
def listitems(d):
|
||
|
return d.items()
|
||
|
|
||
|
if PY3:
|
||
|
def ensure_new_type(obj):
|
||
|
return obj
|
||
|
else:
|
||
|
def ensure_new_type(obj):
|
||
|
from future.types.newbytes import newbytes
|
||
|
from future.types.newstr import newstr
|
||
|
from future.types.newint import newint
|
||
|
from future.types.newdict import newdict
|
||
|
|
||
|
native_type = type(native(obj))
|
||
|
|
||
|
# Upcast only if the type is already a native (non-future) type
|
||
|
if issubclass(native_type, type(obj)):
|
||
|
# Upcast
|
||
|
if native_type == str: # i.e. Py2 8-bit str
|
||
|
return newbytes(obj)
|
||
|
elif native_type == unicode:
|
||
|
return newstr(obj)
|
||
|
elif native_type == int:
|
||
|
return newint(obj)
|
||
|
elif native_type == long:
|
||
|
return newint(obj)
|
||
|
elif native_type == dict:
|
||
|
return newdict(obj)
|
||
|
else:
|
||
|
return obj
|
||
|
else:
|
||
|
# Already a new type
|
||
|
assert type(obj) in [newbytes, newstr]
|
||
|
return obj
|
||
|
|
||
|
|
||
|
__all__ = ['PY2', 'PY26', 'PY3', 'PYPY',
|
||
|
'as_native_str', 'bind_method', 'bord', 'bstr',
|
||
|
'bytes_to_native_str', 'encode_filename', 'ensure_new_type',
|
||
|
'exec_', 'get_next', 'getexception', 'implements_iterator',
|
||
|
'is_new_style', 'isbytes', 'isidentifier', 'isint',
|
||
|
'isnewbytes', 'istext', 'iteritems', 'iterkeys', 'itervalues',
|
||
|
'lfilter', 'listitems', 'listvalues', 'lmap', 'lrange',
|
||
|
'lzip', 'native', 'native_bytes', 'native_str',
|
||
|
'native_str_to_bytes', 'old_div',
|
||
|
'python_2_unicode_compatible', 'raise_',
|
||
|
'raise_with_traceback', 'reraise', 'text_to_native_str',
|
||
|
'tobytes', 'viewitems', 'viewkeys', 'viewvalues',
|
||
|
'with_metaclass'
|
||
|
]
|