Indexing bytes is the problem not slicing.

    value = value.encode('ascii', 'ignore').decode('ascii')

Be cautious if you have to `slice bytestrings`_.

Be cautious if you have to `index bytestrings`_.

.. _slice bytestrings: http://docs.python.org/py3k/howto/pyporting.html#bytes-literals

.. _index bytestrings: http://docs.python.org/py3k/howto/pyporting.html#bytes-literals

Exceptions

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