_compat.py

"""Utilities for writing code that runs on Python 2 and 3"""
# flake8: noqa

# Copyright (c) 2010-2013 Benjamin Peterson
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of
# this software and associated documentation files (the "Software"), to deal in
# the Software without restriction, including without limitation the rights to
# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
# the Software, and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
from __future__ import absolute_import

import operator
import sys
import types

__author__ = "Benjamin Peterson <benjamin@python.org>"
__version__ = "1.3.0"


PY2 = sys.version_info[0] == 2

if not PY2:
    string_types = str,
    integer_types = int,
    class_types = type,
    text_type = str
    binary_type = bytes

    MAXSIZE = sys.maxsize
else:
    string_types = basestring,
    integer_types = (int, long)
    class_types = (type, types.ClassType)
    text_type = unicode
    binary_type = str

    if sys.platform.startswith("java"):
        # Jython always uses 32 bits.
        MAXSIZE = int((1 << 31) - 1)
    else:
        # It's possible to have sizeof(long) != sizeof(Py_ssize_t).
        class X(object):
            def __len__(self):
                return 1 << 31
        try:
            len(X())
        except OverflowError:
            # 32-bit
            MAXSIZE = int((1 << 31) - 1)
        else:
            # 64-bit
            MAXSIZE = int((1 << 63) - 1)
            del X


def _import_module(name):
    """Import module, returning the module after the last dot."""
    __import__(name)
    return sys.modules[name]


if not PY2:
    _iterkeys = "keys"
    _itervalues = "values"
    _iteritems = "items"
    _iterlists = "lists"
else:
    _iterkeys = "iterkeys"
    _itervalues = "itervalues"
    _iteritems = "iteritems"
    _iterlists = "iterlists"


try:
    advance_iterator = next
except NameError:
    def advance_iterator(it):
        return it.next()
next = advance_iterator


try:
    callable = callable
except NameError:
    def callable(obj):
        return any("__call__" in klass.__dict__ for klass in type(obj).__mro__)


def iterkeys(d, **kw):
    """Return an iterator over the keys of a dictionary."""
    return iter(getattr(d, _iterkeys)(**kw))


def itervalues(d, **kw):
    """Return an iterator over the values of a dictionary."""
    return iter(getattr(d, _itervalues)(**kw))


def iteritems(d, **kw):
    """Return an iterator over the (key, value) pairs of a dictionary."""
    return iter(getattr(d, _iteritems)(**kw))


def iterlists(d, **kw):
    """Return an iterator over the (key, [values]) pairs of a dictionary."""
    return iter(getattr(d, _iterlists)(**kw))


if not PY2:
    def b(s):
        return s.encode("latin-1")

    def u(s):
        return s
    if sys.version_info[1] <= 1:
        def int2byte(i):
            return bytes((i,))
    else:
        # This is about 2x faster than the implementation above on 3.2+
        int2byte = operator.methodcaller("to_bytes", 1, "big")
    import io
    StringIO = io.StringIO
    BytesIO = io.BytesIO
else:
    def b(s):  # NOQA
        return s

    def u(s):  # NOQA
        return unicode(s, "unicode_escape")
    int2byte = chr
    import StringIO
    StringIO = BytesIO = StringIO.StringIO


if not PY2:
    import builtins
    exec_ = getattr(builtins, "exec")

    def reraise(tp, value, tb=None):
        if value.__traceback__ is not tb:
            raise value.with_traceback(tb)
        raise value

    del builtins

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_""")

    exec_("""def reraise(tp, value, tb=None):
    raise tp, value, tb
""")

def with_metaclass(meta, base=object):
    """Create a base class with a metaclass."""
    return meta("NewBase", (base,), {})


def get_code(func):
    rv = getattr(func, '__code__', getattr(func, 'func_code', None))
    if rv is None:
        raise TypeError('Could not get code from %r' % type(func).__name__)
    return rv