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Re: Python Sanity Proposal: Type Hinting Solution

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Date Sat, 24 Jan 2015 16:38:48 +1100
Subject Re: Python Sanity Proposal: Type Hinting Solution
From Chris Angelico <rosuav@gmail.com>
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On Sat, Jan 24, 2015 at 4:29 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> Sufficiently clever type-checkers may use assertions to infer types, but
> requiring this is a non-starter.

Or they could use the isinstance checks themselves to infer types.

def func(arg):
    if not isinstance(arg, int): raise ValueError("Expected an integer")

It's fairly straight-forward to do an AST parse on a module, iterate
over it for functions, and then look for a specific pattern like the
above:

If(test=UnaryOp(op=Not(), operand=Call(func=Name(id='isinstance',
ctx=Load()), args=[Name(id='arg', ctx=Load()), Name(id='int',
ctx=Load())], keywords=[], starargs=None, kwargs=None)),
body=[Raise(exc=Call(func=Name(id='ValueError', ctx=Load()),
args=[Str(s='Expected an integer')], keywords=[], starargs=None,
kwargs=None), cause=None)], orelse=[])

... okay, that's not exactly pretty, but it's still a straight-forward
structure. But having just watched a PyCon talk about PyPy and RPython
and type inference, it's pretty clear that static analysis can do a
*lot* more than this; so really, looking for isinstance checks is both
too hard and too simplistic to be really worth doing. Type hinting is
a different beast.

ChrisA

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Thread

Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-22 17:15 -0800
  Re: Python Sanity Proposal: Type Hinting Solution MRAB <python@mrabarnett.plus.com> - 2015-01-23 03:22 +0000
  Re: Python Sanity Proposal: Type Hinting Solution Terry Reedy <tjreedy@udel.edu> - 2015-01-22 22:22 -0500
    Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 11:23 -0800
      Re: Python Sanity Proposal: Type Hinting Solution Christian Gollwitzer <auriocus@gmx.de> - 2015-01-24 22:14 +0100
  Re: Python Sanity Proposal: Type Hinting Solution Rustom Mody <rustompmody@gmail.com> - 2015-01-22 19:23 -0800
    Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 11:36 -0800
  Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-23 14:59 +1100
    Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 11:48 -0800
      Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-24 06:59 +1100
        Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 12:59 -0800
      Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-23 22:02 +0100
        Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 13:59 -0800
          Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-23 23:42 +0100
            Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-23 23:45 +0100
              Re: Python Sanity Proposal: Type Hinting Solution sohcahtoa82@gmail.com - 2015-01-23 14:52 -0800
                Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-24 00:14 +0100
              Re: Python Sanity Proposal: Type Hinting Solution Marko Rauhamaa <marko@pacujo.net> - 2015-01-24 01:52 +0200
                Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-24 16:29 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-24 16:38 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-24 17:36 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-24 17:47 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Marko Rauhamaa <marko@pacujo.net> - 2015-01-24 11:27 +0200
            Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 15:39 -0800
            Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-25 00:29 +1100
              Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-24 15:09 +0100
                Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-24 15:32 +0100
                Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-25 03:05 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Marco Buttu <marco.buttu@gmail.com> - 2015-01-24 15:25 +0100
              Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-24 08:41 -0800
                Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-25 04:26 +1100
                Re: Python Sanity Proposal: Type Hinting Solution Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-24 17:36 +0000
                Re: Python Sanity Proposal: Type Hinting Solution Paul Rubin <no.email@nospam.invalid> - 2015-01-24 09:37 -0800
                Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-25 06:59 +1100
  Re: Python Sanity Proposal: Type Hinting Solution Terry Reedy <tjreedy@udel.edu> - 2015-01-23 00:03 -0500
    Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-23 16:59 +1100
      Re: Python Sanity Proposal: Type Hinting Solution "Fetchinson ." <fetchinson@googlemail.com> - 2015-01-23 14:23 +0100
        Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 12:21 -0800
          Re: Python Sanity Proposal: Type Hinting Solution Mario Figueiredo <marfig@gmail.com> - 2015-01-23 22:12 +0100
            Re: Python Sanity Proposal: Type Hinting Solution Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-23 14:26 -0800
        Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-24 17:21 +1100
          Re: Python Sanity Proposal: Type Hinting Solution Tim Chase <python.list@tim.thechases.com> - 2015-01-24 06:47 -0600
            Re: Python Sanity Proposal: Type Hinting Solution Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-25 00:40 +1100
              Re: Python Sanity Proposal: Type Hinting Solution Roy Smith <roy@panix.com> - 2015-01-24 09:06 -0500
          Re: Python Sanity Proposal: Type Hinting Solution "Fetchinson ." <fetchinson@googlemail.com> - 2015-01-24 22:01 +0100
      Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-24 04:11 +1100
      Re: Python Sanity Proposal: Type Hinting Solution "Fetchinson ." <fetchinson@googlemail.com> - 2015-01-23 22:07 +0100
  Re: Python Sanity Proposal: Type Hinting Solution Chris Angelico <rosuav@gmail.com> - 2015-01-23 16:31 +1100

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