future doesn't support python3 functions annotations

[matclab]

I just tried future on a python3 program and it fails on python3 functions annotations (http://www.python.org/dev/peps/pep-3107/) :

    def _parse(self, filename: str, dir='.') -> list:
                             ^
SyntaxError: invalid syntax

I'm not sure if there is a way to fix this.

[edschofield]

Hi @matclab,

Thanks for reporting this. Yes, this is a known limitation. Any Python 3-only syntax will fail to run on Python 2; importing future cannot help with this because Python won't even attempt to run code that generates a SyntaxError.

The futurize script could potentially convert function annotations into the following syntax, which is compatible with both Py2 and Py3 (using your example)::

def _parse(self, filename, dir='.'):
    ...
_parse.__annotations__ = {'filename': str, 'return': list}

Would this meet your use-case? I have filed this as a feature request in issue #3.

[matclab]

I may give a try, but I can not see why it won't work for my use case…
Thanks for having considered it.