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docs/func_annotations.rst
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Ed Schofield
Update docs: use sphinx-bootstrap and include basic auto-generated API docs
14 ноя 2013, 16:25
14 ноя 2013, 16:25
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.. _func_annotations: Function annotations ==================== Function annotations are a piece of syntax introduced in Python 3.0 that was not backported to Python 2.x. (See PEP 3107: http://www.python.org/dev/peps/pep-3107/). They cause Python 2 to raise a SyntaxError. To rewrite Python 3 code with function annotations to be compatible with both Python 3 and Python 2, you can replace the annotation syntax with a dictionary called ``__annotations__`` as an attribute on your functions. For example, code such as this:: def _parse(self, filename: str, dir='.') -> list: pass can be re-expressed like this:: def _parse(self, filename, dir='.'): pass _parse.__annotations__ = {'filename': str, 'return': list} As described in PEP 3107, the annotation for a function's return value corresponds to the ``'return'`` key in the dictionary. (Note that PEP 3107 describes annotations as belonging to a ``func_annotations`` attribute. This attribute was renamed in Python 3.2 to ``__annotations__``.) Be aware that some libraries that consume function annotations, such as `Reticulated <https://github.com/mvitousek/reticulated>`_, have their own semantics for supporting earlier Python versions, such as decorators. If you are using such a library, please use its own mechanism for providing compatibility with earlier Python versions, rather than the generic equivalent above.