python/helpers/coverage/backward.py

"""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=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.version_info >= (3, 0):
    def exec_code_object(code, global_map):
        """A wrapper around exec()."""
        exec(code, 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_code_object(code, global_map):\n"
            "    exec code in global_map\n",
            "<exec_function>", "exec"
            )
        )

# ConfigParser was renamed to the more-standard configparser
try:
    import configparser
except ImportError:
    import ConfigParser as configparser

# Python 3.2 provides `tokenize.open`, the best way to open source files.
try:
    import tokenize
    open_source = tokenize.open     # pylint: disable=E1101
except AttributeError:
    def open_source(fname):
        """Open a source file the best way."""
        return open(fname, "rU")

# Python 3.x is picky about bytes and strings, so provide methods to
# get them right, and make them no-ops in 2.x
if sys.version_info >= (3, 0):
    def to_bytes(s):
        """Convert string `s` to bytes."""
        return s.encode('utf8')

    def to_string(b):
        """Convert bytes `b` to a string."""
        return b.decode('utf8')

else:
    def to_bytes(s):
        """Convert string `s` to bytes (no-op in 2.x)."""
        return s

    def to_string(b):
        """Convert bytes `b` to a string (no-op in 2.x)."""
        return b

# Md5 is available in different places.
try:
    import hashlib
    md5 = hashlib.md5
except ImportError:
    import md5
    md5 = md5.new