[Python-ideas] Should bool continue to inherit from int?

Chris Barker chris.barker at noaa.gov
Wed Jan 21 21:12:10 CET 2015

On Wed, Jan 21, 2015 at 11:11 AM, Guido van Rossum <guido at python.org> wrote:

> So I believe you are saying, suppose I have a function that takes an
> integer argument and then JSON-encodes it and sends it to some server that
> requires a JSON int. Now suppose you are adding type hints to your code,
> and you add ": int" to the parameter under discussion. And now suppose you
> have a faulty caller which calls this function with the argument set to
> True. This program will type-check correctly, because True is a bool which
> is a subclass of int, but it will run incorrectly, because (under this
> assumption) True will be converted to a JSON true value, which the server
> rejects.

This sounds like it may benefit from the issue under discussion for Cython
-- a way to specify an int only, and not allow subclasses.

Though I suppose in this case, you may want to allow other subclasses, just
not that one.

This hypothetical code could also to a cast/conversion to int anyway, which
is pretty much how you'd do it with duck typing and no type checking.



Christopher Barker, Ph.D.

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Chris.Barker at noaa.gov
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