Strings in Python. Credit to @lsemel

strings.py

"""
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        * You do not know the encoding of a string. It could be ASCII or UTF-8.
          There is no way to tell.

        * Python will assume ASCII encoding when converting from strings to unicode
          and throw an error if it encounters an illegal character, such as if you
          just encoded UTF-8 into a string (by using smart_str, for instance).

        * You should generally not have to do any encoding into strings.  Django takes
          care of providing Unicode objects, and encoding appropriately whenever
          it outputs anything (to the response, or to the database)

        * Think of strings as a byte array, and Unicode as some sort of internal object (say, a linked list) that
          you can't input or output without encoding or decoding

>>> from django.utils.encoding import smart_str
>>> 'a'+'b'                 # Two bytes, assumed to be ASCII
'ab'
>>> u'a'+u'b'               # Two unicode characters
u'ab'
>>> 'a'+u'b'                # The byte 'a' is converted to Unicode, under the assumption it represents ASCII
u'ab'
>>> smart_str('a')          # Does nothing
'a'
>>> smart_str(u'a')                 # The Unicode character 'a' encoded as bytes
'a'
>>> smart_str(u'\u00ff')            # Another unicode character, encoded as bytes
'\xc3\xbf'
>>> smart_str(u'\u00ff') + 'aa'         # Concatenating two sets of two bytes each
'\xc3\xbfaa'
>>> smart_str(u'\u00ff') +  u'aa'       # Tries to convert those bytes to Unicode, assuming they are ASCII
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 0: ordinal not in range(128)

>>> smart_str(u'\u00ff').decode('utf-8') +  u'aa'  # Tell Python those bytes are not ASCII, but are UTF-8
u'\xffaa'
"""