python-future/future/utils/__init__.py at native_stdlib · dev-zero/python-future · GitHub

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"""

A selection of cross-compatible functions for Python 2 and 3.

These come from several sources:

* Jinja2 (BSD licensed: see https://github.com/mitsuhiko/jinja2/blob/master/LICENSE

* Pandas compatibility module pandas.compat

* six.py by Benjamin Peterson

* Django

This exports useful functions for 2/3 compatible code that are not

builtins on Python 3:

* bind_method: binds functions to classes

* ``native_str_to_bytes`` and ``bytes_to_native_str``

* ``native_str``: always equal to the native platform string object (because

this may be shadowed by imports from future.builtins)

* lists: lrange(), lmap(), lzip(), lfilter()

* iterable method compatibility: iteritems, iterkeys, itervalues

* Uses the original method if available, otherwise uses items, keys, values.

* types:

* text_type: unicode in Python 2, str in Python 3

* binary_type: str in Python 2, bythes in Python 3

* string_types: basestring in Python 2, str in Python 3

* bchr(c):

Take an integer and make a 1-character byte string

* bord(c)

Take the result of indexing on a byte string and make an integer

* tobytes(s)

Take a text string, a byte string, or a sequence of characters taken

from a byte string, and make a byte string.

This module also defines a simple decorator called

``python_2_unicode_compatible`` (from django.utils.encoding) which

defines ``__unicode__`` and ``__str__`` methods consistently under Python

3 and 2. To support Python 3 and 2 with a single code base, simply define

a ``__str__`` method returning unicode text and apply the

python_2_unicode_compatible decorator to the class like this::

>>> from future.utils import python_2_unicode_compatible

>>> @python_2_unicode_compatible

... class MyClass(object):

... def __str__(self):

... return u'Unicode string: \u5b54\u5b50'

>>> a = MyClass()

Then, after this import:

>>> from future.builtins import str

the following is ``True`` on both Python 3 and 2::

>>> str(a) == a.encode('utf-8').decode('utf-8')

True

and, on a Unicode-enabled terminal with the right fonts, these both print the

Chinese characters for Confucius::

print(a)

print(str(a))

On Python 3, this decorator is a no-op.

"""

import types

import sys

import numbers

import functools

PY3 = sys.version_info[0] == 3

PY2 = sys.version_info[0] == 2

PY26 = sys.version_info[0:2] == (2, 6)

PYPY = hasattr(sys, 'pypy_translation_info')

def python_2_unicode_compatible(cls):

"""

A decorator that defines __unicode__ and __str__ methods under Python

2. Under Python 3 it does nothing.

To support Python 2 and 3 with a single code base, define a __str__

method returning unicode text and apply this decorator to the class.

The implementation comes from django.utils.encoding.

"""

if not PY3:

cls.__unicode__ = cls.__str__

cls.__str__ = lambda self: self.__unicode__().encode('utf-8')

return cls

def with_metaclass(meta, *bases):

"""

Function from jinja2/_compat.py. License: BSD.

Use it like this::

class BaseForm(object):

pass

class FormType(type):

pass

class Form(with_metaclass(FormType, BaseForm)):

pass

This requires a bit of explanation: the basic idea is to make a

dummy metaclass for one level of class instantiation that replaces

itself with the actual metaclass. Because of internal type checks

we also need to make sure that we downgrade the custom metaclass

for one level to something closer to type (that's why __call__ and

__init__ comes back from type etc.).

This has the advantage over six.with_metaclass of not introducing

dummy classes into the final MRO.

"""

class metaclass(meta):

__call__ = type.__call__

__init__ = type.__init__

def __new__(cls, name, this_bases, d):

if this_bases is None:

return type.__new__(cls, name, (), d)

return meta(name, bases, d)

return metaclass('temporary_class', None, {})

# Definitions from pandas.compat follow:

if PY3:

def bchr(s):

return bytes([s])

def bstr(s):

if isinstance(s, str):

return bytes(s, 'latin-1')

else:

return bytes(s)

def bord(s):

return s

else:

# Python 2

def bchr(s):

return chr(s)

def bstr(s):

return str(s)

def bord(s):

return ord(s)

###

if PY3:

def tobytes(s):

if isinstance(s, bytes):

return s

else:

if isinstance(s, str):

return s.encode('latin-1')

else:

return bytes(s)

else:

# Python 2

def tobytes(s):

'''

Encodes to latin-1 (where the first 256 chars are the same as

ASCII.)

'''

if isinstance(s, unicode):

return s.encode('latin-1')

else:

return ''.join(s)

if PY3:

def native_str_to_bytes(s, encoding='ascii'):

return s.encode(encoding)

def bytes_to_native_str(b, encoding='ascii'):

return b.decode(encoding)

def text_to_native_str(b, encoding='ascii'):

return b

else:

# Python 2

def native_str_to_bytes(s, encoding='ascii'):

return s

def bytes_to_native_str(b, encoding='ascii'):

return b

def text_to_native_str(b, encoding='ascii'):

"""

Use this to create a Py2 native string when "from __future__ import

unicode_literals" is in effect.

"""

return b.encode(encoding)

if PY3:

# list-producing versions of the major Python iterating functions

def lrange(*args, **kwargs):

return list(range(*args, **kwargs))

def lzip(*args, **kwargs):

return list(zip(*args, **kwargs))

def lmap(*args, **kwargs):

return list(map(*args, **kwargs))

def lfilter(*args, **kwargs):

return list(filter(*args, **kwargs))

else:

import __builtin__

# Python 2-builtin ranges produce lists

lrange = __builtin__.range

lzip = __builtin__.zip

lmap = __builtin__.map

lfilter = __builtin__.filter

def isidentifier(s, dotted=False):

'''

A function equivalent to the str.isidentifier method on Py3

'''

if dotted:

return all(isidentifier(a) for a in s.split('.'))

if PY3:

return s.isidentifier()

else:

import re

_name_re = re.compile(r"[a-zA-Z_][a-zA-Z0-9_]*$")

return bool(_name_re.match(s))

def viewitems(obj, **kwargs):

"""

Function for iterating over dictionary items with the same set-like

behaviour on Py2.7 as on Py3.

Passes kwargs to method."""

func = getattr(obj, "viewitems", None)

if not func:

func = obj.items

return func(**kwargs)

def viewkeys(obj, **kwargs):

"""

Function for iterating over dictionary keys with the same set-like

behaviour on Py2.7 as on Py3.

Passes kwargs to method."""

func = getattr(obj, "viewkeys", None)

if not func:

func = obj.keys

return func(**kwargs)

def viewvalues(obj, **kwargs):

"""

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 bound/unbound method issue

if not PY3:

setattr(cls, name, types.MethodType(func, None, cls))

else:

setattr(cls, name, func)

def getexception():

return sys.exc_info()[1]

if PY3:

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)

def raise_with_traceback(exc, traceback=Ellipsis):

if traceback == Ellipsis:

_, _, traceback = sys.exc_info()

raise exc.with_traceback(traceback)

else:

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.builtins.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 future.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""")

def old_div(a, b):

"""

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

__all__ = ['PY3', 'PY2', 'PYPY', 'python_2_unicode_compatible',

'as_native_str',

'with_metaclass', 'bchr', 'bstr', 'bord',

'tobytes', 'str_to_native_bytes', 'bytes_to_native_str',

'lrange', 'lmap', 'lzip', 'lfilter',

'isidentifier', 'iteritems', 'iterkeys', 'itervalues',

'viewitems', 'viewkeys', 'viewvalues',

'bind_method', 'getexception',

'reraise', 'implements_iterator', 'get_next', 'encode_filename',

'is_new_style', 'native_str', 'old_div', 'as_native_str'

]

python-future/future/utils/__init__.py at native_stdlib · dev-zero/python-future · GitHub

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python-future/future/utils/init.py at native_stdlib · dev-zero/python-future · GitHub

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