six / six.py

"""Utilities for writing code that runs on Python 2 and 3"""

import operator
import sys
import types

__author__ = "Benjamin Peterson <benjamin@python.org>"
__version__ = "1.2.0"


# True if we are running on Python 3.
PY3 = sys.version_info[0] == 3

if PY3:
    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 _add_doc(func, doc):
    """Add documentation to a function."""
    func.__doc__ = doc


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


class _LazyDescr(object):

    def __init__(self, name):
        self.name = name

    def __get__(self, obj, tp):
        result = self._resolve()
        setattr(obj, self.name, result)
        # This is a bit ugly, but it avoids running this again.
        delattr(tp, self.name)
        return result


class MovedModule(_LazyDescr):

    def __init__(self, name, old, new=None):
        super(MovedModule, self).__init__(name)
        if PY3:
            if new is None:
                new = name
            self.mod = new
        else:
            self.mod = old

    def _resolve(self):
        return _import_module(self.mod)


class MovedAttribute(_LazyDescr):

    def __init__(self, name, old_mod, new_mod, old_attr=None, new_attr=None):
        super(MovedAttribute, self).__init__(name)
        if PY3:
            if new_mod is None:
                new_mod = name
            self.mod = new_mod
            if new_attr is None:
                if old_attr is None:
                    new_attr = name
                else:
                    new_attr = old_attr
            self.attr = new_attr
        else:
            self.mod = old_mod
            if old_attr is None:
                old_attr = name
            self.attr = old_attr

    def _resolve(self):
        module = _import_module(self.mod)
        return getattr(module, self.attr)



class _MovedItems(types.ModuleType):
    """Lazy loading of moved objects"""


_moved_attributes = [
    MovedAttribute("cStringIO", "cStringIO", "io", "StringIO"),
    MovedAttribute("filter", "itertools", "builtins", "ifilter", "filter"),
    MovedAttribute("input", "__builtin__", "builtins", "raw_input", "input"),
    MovedAttribute("map", "itertools", "builtins", "imap", "map"),
    MovedAttribute("reload_module", "__builtin__", "imp", "reload"),
    MovedAttribute("reduce", "__builtin__", "functools"),
    MovedAttribute("StringIO", "StringIO", "io"),
    MovedAttribute("xrange", "__builtin__", "builtins", "xrange", "range"),
    MovedAttribute("zip", "itertools", "builtins", "izip", "zip"),

    MovedModule("builtins", "__builtin__"),
    MovedModule("configparser", "ConfigParser"),
    MovedModule("copyreg", "copy_reg"),
    MovedModule("http_cookiejar", "cookielib", "http.cookiejar"),
    MovedModule("http_cookies", "Cookie", "http.cookies"),
    MovedModule("html_entities", "htmlentitydefs", "html.entities"),
    MovedModule("html_parser", "HTMLParser", "html.parser"),
    MovedModule("http_client", "httplib", "http.client"),
    MovedModule("BaseHTTPServer", "BaseHTTPServer", "http.server"),
    MovedModule("CGIHTTPServer", "CGIHTTPServer", "http.server"),
    MovedModule("SimpleHTTPServer", "SimpleHTTPServer", "http.server"),
    MovedModule("cPickle", "cPickle", "pickle"),
    MovedModule("queue", "Queue"),
    MovedModule("reprlib", "repr"),
    MovedModule("socketserver", "SocketServer"),
    MovedModule("tkinter", "Tkinter"),
    MovedModule("tkinter_dialog", "Dialog", "tkinter.dialog"),
    MovedModule("tkinter_filedialog", "FileDialog", "tkinter.filedialog"),
    MovedModule("tkinter_scrolledtext", "ScrolledText", "tkinter.scrolledtext"),
    MovedModule("tkinter_simpledialog", "SimpleDialog", "tkinter.simpledialog"),
    MovedModule("tkinter_tix", "Tix", "tkinter.tix"),
    MovedModule("tkinter_constants", "Tkconstants", "tkinter.constants"),
    MovedModule("tkinter_dnd", "Tkdnd", "tkinter.dnd"),
    MovedModule("tkinter_colorchooser", "tkColorChooser",
                "tkinter.colorchooser"),
    MovedModule("tkinter_commondialog", "tkCommonDialog",
                "tkinter.commondialog"),
    MovedModule("tkinter_tkfiledialog", "tkFileDialog", "tkinter.filedialog"),
    MovedModule("tkinter_font", "tkFont", "tkinter.font"),
    MovedModule("tkinter_messagebox", "tkMessageBox", "tkinter.messagebox"),
    MovedModule("tkinter_tksimpledialog", "tkSimpleDialog",
                "tkinter.simpledialog"),
    MovedModule("urllib_robotparser", "robotparser", "urllib.robotparser"),
    MovedModule("winreg", "_winreg"),
]
for attr in _moved_attributes:
    setattr(_MovedItems, attr.name, attr)
del attr

moves = sys.modules[__name__ + ".moves"] = _MovedItems("moves")


def add_move(move):
    """Add an item to six.moves."""
    setattr(_MovedItems, move.name, move)


def remove_move(name):
    """Remove item from six.moves."""
    try:
        delattr(_MovedItems, name)
    except AttributeError:
        try:
            del moves.__dict__[name]
        except KeyError:
            raise AttributeError("no such move, %r" % (name,))


if PY3:
    _meth_func = "__func__"
    _meth_self = "__self__"

    _func_code = "__code__"
    _func_defaults = "__defaults__"

    _iterkeys = "keys"
    _itervalues = "values"
    _iteritems = "items"
else:
    _meth_func = "im_func"
    _meth_self = "im_self"

    _func_code = "func_code"
    _func_defaults = "func_defaults"

    _iterkeys = "iterkeys"
    _itervalues = "itervalues"
    _iteritems = "iteritems"


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


if PY3:
    def get_unbound_function(unbound):
        return unbound

    Iterator = object

    def callable(obj):
        return any("__call__" in klass.__dict__ for klass in type(obj).__mro__)
else:
    def get_unbound_function(unbound):
        return unbound.im_func

    class Iterator(object):

        def next(self):
            return type(self).__next__(self)

    callable = callable
_add_doc(get_unbound_function,
         """Get the function out of a possibly unbound function""")


get_method_function = operator.attrgetter(_meth_func)
get_method_self = operator.attrgetter(_meth_self)
get_function_code = operator.attrgetter(_func_code)
get_function_defaults = operator.attrgetter(_func_defaults)


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

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

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


if PY3:
    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):
        return s
    def u(s):
        return unicode(s, "unicode_escape")
    int2byte = chr
    import StringIO
    StringIO = BytesIO = StringIO.StringIO
_add_doc(b, """Byte literal""")
_add_doc(u, """Text literal""")


if PY3:
    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


    print_ = getattr(builtins, "print")
    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 print_(*args, **kwargs):
        """The new-style print function."""
        fp = kwargs.pop("file", sys.stdout)
        if fp is None:
            return
        def write(data):
            if not isinstance(data, basestring):
                data = str(data)
            fp.write(data)
        want_unicode = False
        sep = kwargs.pop("sep", None)
        if sep is not None:
            if isinstance(sep, unicode):
                want_unicode = True
            elif not isinstance(sep, str):
                raise TypeError("sep must be None or a string")
        end = kwargs.pop("end", None)
        if end is not None:
            if isinstance(end, unicode):
                want_unicode = True
            elif not isinstance(end, str):
                raise TypeError("end must be None or a string")
        if kwargs:
            raise TypeError("invalid keyword arguments to print()")
        if not want_unicode:
            for arg in args:
                if isinstance(arg, unicode):
                    want_unicode = True
                    break
        if want_unicode:
            newline = unicode("\n")
            space = unicode(" ")
        else:
            newline = "\n"
            space = " "
        if sep is None:
            sep = space
        if end is None:
            end = newline
        for i, arg in enumerate(args):
            if i:
                write(sep)
            write(arg)
        write(end)

_add_doc(reraise, """Reraise an exception.""")


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