futurize and pasteurize are useful to automate much of the work of porting, particularly the boring repetitive text substitutions. They also help to flag which parts of the code require attention.

Nevertheless, futurize and pasteurize are still incomplete and make some mistakes, like 2to3, on which they are based. Please report bugs on GitHub. Contributions to the lib2to3-based fixers for futurize and pasteurize are particularly welcome! Please see :ref:`contributing`.

futurize doesn't currently make the following change automatically:

1. Strings containing \U produce a SyntaxError on Python 3. An example is:

   s = 'C:\Users'.
   

   Python 2 expands this to s = 'C:\\Users', but Python 3 requires a raw prefix (r'...'). This also applies to multi-line strings (including multi-line docstrings).

Also see the tests in future/tests/test_futurize.py marked @expectedFailure or @skip for known limitations.