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# module which helps with porting to Python 3
#
# Copyright (C) Lumir Balhar <lbalhar@redhat.com> 2017
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""module which helps with porting to Python 3"""
import sys
PY3 = sys.version_info[0] == 3
if PY3:
# Sometimes in PY3 we have variables whose content can be 'bytes' or
# 'str' and we can't be sure which. Generally this is because the
# code variable can be initialised (or reassigned) a value from different
# api(s) or functions depending on complex conditions or logic. Or another
# common case is in PY2 the variable is 'type <str>' and in PY3 it is
# 'class <str>' and the function to use e.g. b64encode requires 'bytes'
# in PY3. In such cases it would be nice to avoid excessive testing in
# the client code. Calling such a helper function should be avoided
# if possible but sometimes this just isn't possible.
# If a 'str' object is passed in it is encoded using 'utf8' or if 'bytes'
# is passed in it is returned unchanged.
# Using this function is PY2/PY3 code should ensure in most cases
# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
# encodes the variable (see PY2 implementation of this function below)
def get_bytes(bytesorstring):
tmp = bytesorstring
if isinstance(bytesorstring, str):
tmp = bytesorstring.encode('utf8')
elif not isinstance(bytesorstring, bytes):
raise ValueError('Expected byte or string for %s:%s' % (type(bytesorstring), bytesorstring))
return tmp
# helper function to get a string from a variable that maybe 'str' or
# 'bytes' if 'bytes' then it is decoded using 'utf8'. If 'str' is passed
# it is returned unchanged
# Using this function is PY2/PY3 code should ensure in most cases
# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
# decodes the variable (see PY2 implementation of this function below)
def get_string(bytesorstring):
tmp = bytesorstring
if isinstance(bytesorstring, bytes):
tmp = bytesorstring.decode('utf8')
elif not isinstance(bytesorstring, str):
raise ValueError('Expected byte of string for %s:%s' % (type(bytesorstring), bytesorstring))
return tmp
def cmp_fn(x, y):
"""
Replacement for built-in function cmp that was removed in Python 3
Compare the two objects x and y and return an integer according to
the outcome. The return value is negative if x < y, zero if x == y
and strictly positive if x > y.
"""
return (x > y) - (x < y)
# compat functions
from functools import cmp_to_key as cmp_to_key_fn
# compat types
integer_types = int,
string_types = str
text_type = str
binary_type = bytes
# alias
import io
StringIO = io.StringIO
def ConfigParser(defaults=None, dict_type=dict, allow_no_value=False):
from configparser import ConfigParser
return ConfigParser(defaults, dict_type, allow_no_value, interpolation=None)
else:
# Helper function to return bytes.
# if 'unicode' is passed in then it is decoded using 'utf8' and
# the result returned. If 'str' is passed then it is returned unchanged.
# Using this function is PY2/PY3 code should ensure in most cases
# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
# encodes the variable (see PY3 implementation of this function above)
def get_bytes(bytesorstring):
tmp = bytesorstring
if isinstance(bytesorstring, unicode):
tmp = bytesorstring.encode('utf8')
elif not isinstance(bytesorstring, str):
raise ValueError('Expected string for %s:%s' % (type(bytesorstring), bytesorstring))
return tmp
# Helper function to return string.
# if 'str' or 'unicode' passed in they are returned unchanged
# otherwise an exception is generated
# Using this function is PY2/PY3 code should ensure in most cases
# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
# decodes the variable (see PY3 implementation of this function above)
def get_string(bytesorstring):
tmp = bytesorstring
if not(isinstance(bytesorstring, str) or isinstance(bytesorstring, unicode)):
raise ValueError('Expected str or unicode for %s:%s' % (type(bytesorstring), bytesorstring))
return tmp
if sys.version_info < (2, 7):
def cmp_to_key_fn(mycmp):
"""Convert a cmp= function into a key= function"""
class K(object):
__slots__ = ['obj']
def __init__(self, obj, *args):
self.obj = obj
def __lt__(self, other):
return mycmp(self.obj, other.obj) < 0
def __gt__(self, other):
return mycmp(self.obj, other.obj) > 0
def __eq__(self, other):
return mycmp(self.obj, other.obj) == 0
def __le__(self, other):
return mycmp(self.obj, other.obj) <= 0
def __ge__(self, other):
return mycmp(self.obj, other.obj) >= 0
def __ne__(self, other):
return mycmp(self.obj, other.obj) != 0
def __hash__(self):
raise TypeError('hash not implemented')
return K
else:
from functools import cmp_to_key as cmp_to_key_fn
# compat types
integer_types = (int, long)
string_types = basestring
text_type = unicode
binary_type = str
# alias
import cStringIO
StringIO = cStringIO.StringIO
from ConfigParser import ConfigParser
cmp_fn = cmp
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