2017-11-26 6:00 GMT-05:00 Kirill Balunov <kirillbalu...@gmail.com>: > Hi! > > 2017-11-26 4:31 GMT+03:00 Juan Nunez-Iglesias <jni.s...@gmail.com>: > >> >> On 26 Nov 2017, 12:27 PM +1100, Nathaniel Smith <n...@pobox.com>, wrote: >> >> It turns out that the PEP 484 type system is *mostly* not useful for >> this. They're really designed for checking consistency across a large >> code-base, not for enabling compiler speedups. For example, if you >> annotate something as an int, that means "this object is a subclass of >> int". This is enough to let mypy catch your mistake if you >> accidentally pass in a float instead, but it's not enough to tell you >> anything at all about the object's behavior -- you could make a wacky >> int subclass that acts like a string or something. >> >> > I have subscribed to many lists, although I am not an active participant > in them. Nevertheless this topic of using the type annotation in their > projects was discussed several times on all Cython-like channels (and it > becomes much more acute now days). "Misconceptions" arise both for ordinary > users and developers, but I have never seen anyone to write clearly why the > application of type annotation in Cython (and similar projects) is > impossible or not reasonable. Maybe someone close to the topic has the time > and energy to sum up and write a brief summary of how to perceive them and > why they should be viewed "orthogonal"? > > Maybe I'm looking too superficially at this topic. But both Mypy and > Cython perform type checking. From the Cython point of view I do not see > any pitfalls, type checking and type conversions are what Cython is doing > right now during compilation (and looks at types as strictly as necessary). > From Mypy's point of view, it's possible that it can delegate all this > stuff, using a certain option, on a project's related type checker (which > can be much stricter in its assumptions) > The main (perceived) difficulty is that the type systems are different. If Cython has a list-typed argument, it wants exactly a list so it can use specialized code for lists, but to mypy it means "list or a subclass of list", which is not as easily optimized because the subclass may do things differently from the base class. Similarly, to Cython an int means a C int, and in Python it may mean an arbitrary-precision integer.
However, Cython managed to overcome the problem and actually added support for type annotations recently; see https://github.com/cython/cython/issues/1672 and https://github.com/cython/cython/issues/1850. I haven't used the support myself and there are probably still details to be worked out, but in principle it should be possible to use both Cython and mypy on a codebase. > > With kind regards, -gdg > > > > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion > >
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