[Python-Dev] Type hints -- a mediocre programmer's reaction (original) (raw)

Chris Angelico rosuav at gmail.com
Tue Apr 21 11:10:40 CEST 2015

On Tue, Apr 21, 2015 at 6:58 PM, Cory Benfield <cory at lukasa.co.uk> wrote:

On 21 April 2015 at 01:45, Chris Angelico <rosuav at gmail.com> wrote:

When you're writing a library, it can be a great help to provide type annotations, because every application that uses your library can benefit. It can be a great help to whom? Not to me (the library author), because I can't use them in my library code, because I have to support 2.7. That's by no means a bad thing (after all, most libraries are written to help others), but I found it really unclear who was being advantaged here.

Mainly application users get the benefit, I expect. But I may be wrong.

... That's got nothing on the type of the files argument, which is the most incredibly polymorphic argument I've ever seen: the best I can work out it would be:

Optional[ Union[ Mapping[ basestring, Union[ Tuple[basestring, Optional[Union[basestring, file]]], Tuple[basestring, Optional[Union[basestring, file]], Optional[basestring]], Tuple[basestring, Optional[Union[basestring, file]], Optional[basestring], Optional[Headers]] ] ], Iterable[ Tuple[ basestring, Union[ Tuple[basestring, Optional[Union[basestring, file]]], Tuple[basestring, Optional[Union[basestring, file]], Optional[basestring]], Tuple[basestring, Optional[Union[basestring, file]], Optional[basestring], Optional[Headers]] ] ] ] ]

At this point, you may want to just stop caring about the exact type. Part of the point of gradual typing is that you can short-cut a lot of this. And quite frankly, this isn't really helping anything. Just skip it and say that it's Union[Mapping, Iterable, None].

ChrisA

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