"""Add things to old Pythons so I can pretend they are newer."""

# This file does lots of tricky stuff, so disable a bunch of lintisms.
# pylint: disable-msg=F0401,W0611,W0622
# F0401: Unable to import blah
# W0611: Unused import blah
# W0622: Redefining built-in blah

import os, sys

# Python 2.3 doesn't have `set`
try:
    set = set       # new in 2.4
except NameError:
    from sets import Set as set


# Python 2.3 doesn't have `sorted`.
try:
    sorted = sorted
except NameError:
    def sorted(iterable):
        """A 2.3-compatible implementation of `sorted`."""
        lst = list(iterable)
        lst.sort()
        return lst

# Pythons 2 and 3 differ on where to get StringIO

try:
    from cStringIO import StringIO
    BytesIO = StringIO
except ImportError:
    from io import StringIO, BytesIO

# What's a string called?

try:
    string_class = basestring
except NameError:
    string_class = str

# Where do pickles come from?

try:
    import cPickle as pickle
except ImportError:
    import pickle

# range or xrange?

try:
    range = xrange
except NameError:
    range = range

# Exec is a statement in Py2, a function in Py3

if sys.hexversion > 0x03000000:
    def exec_function(source, filename, global_map):
        """A wrapper around exec()."""
        exec(compile(source, filename, "exec"), global_map)
else:
    # OK, this is pretty gross.  In Py2, exec was a statement, but that will
    # be a syntax error if we try to put it in a Py3 file, even if it is never
    # executed.  So hide it inside an evaluated string literal instead.
    eval(compile("""\
def exec_function(source, filename, global_map):
    exec compile(source, filename, "exec") in global_map
""",
    "<exec_function>", "exec"
    ))
