[Python-ideas] Proposal: Use mypy syntax for function annotations

Andrey Vlasovskikh andrey.vlasovskikh at gmail.com
Wed Aug 13 23:08:33 CEST 2014

2014-08-14, 0:19, Guido van Rossum <guido at python.org> wrote:

> Yesterday afternoon I had an inspiring conversation with Bob Ippolito (man of many trades, author of simplejson) and Jukka Lehtosalo (author of mypy: http://mypy-lang.org/). Bob gave a talk at EuroPython about what Python can learn from Haskell (and other languages); yesterday he gave the same talk at Dropbox. The talk is online (https://ep2014.europython.eu/en/schedule/sessions/121/) and in broad strokes comes down to three suggestions:
>  (a) Python should adopt mypy's syntax for function annotations

+1. I'm a developer of the code analysis engine of PyCharm. I have discussed this idea with Jukka Lehtosalo and recently with Dave Halter, the author of Jedi code completion library. Standardized type annotations would be very useful for code analysis tools and IDEs such as PyCharm, Jedi and pylint. Type annotations would be especially great for third-party libraries. The idea is that most Python programmers don't have to write annotations in order to benefit from them. Annotated libraries are often enough for good code analysis.

We (PyCharm) and Jukka have made some initial steps in this direction, including thoughts on semantics of annotations (https://github.com/pytypes/pytypes). Feedback is welcome.

Here are slides from my talk about optional typing in Python, that show how Mypy types can be used in both static and dynamic type checking (http://blog.pirx.ru/media/files/2013/python-optional-typing/), Mypy-related part starts from slide 14.

We are interested in getting type annotations standardized and we would like to help developing and testing type annotations proposals.

Andrey Vlasovskikh
Web: http://pirx.ru/

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