Portable bytes and unicode for Python 2.x and 3.x

bu.py

import sys


DEFAULT_CHARSET = 'utf-8'


if sys.version_info >= (3, 0):
    def b(string, charset=DEFAULT_CHARSET):
        if isbytes(string):
            return bytes(string)
        else:
            return bytes(str(string), charset)
else:
    def b(string, charset=DEFAULT_CHARSET):
        if isinstance(string, unicode):
            return string.encode(charset)
        else:
            return str(string)


if sys.version_info >= (3, 0):
    def u(string, charset=DEFAULT_CHARSET):
        if isbytes(string):
            return string.decode(charset)
        else:
            return str(string)
else:
    def u(string, charset=DEFAULT_CHARSET):
        if isinstance(string, unicode):
            return string
        elif hasattr(string, '__unicode__'):
            return unicode(string)
        else:
            return str(string).decode(charset)


def isbytes(obj):
    return isinstance(obj, bytes) and not isinstance(obj, str)