syntax difference (type hints)

[Dan Strohl]

> -----Original Message-----
> From: Python-list <python-list-bounces+d.strohl=f5.com at python.org> On
> Behalf Of Schachner, Joseph
> Sent: Monday, June 18, 2018 7:58 AM
> To: Ed Kellett <e+python-list at kellett.im>; python-list at python.org
> Subject: RE: syntax difference (type hints)
> 
> EXTERNAL MAIL: python-list-bounces+d.strohl=f5.com at python.org
> 
> Assuming that we want Python to remain a dynamically typed (but strongly
> typed) language, I believe the proposed type hints are only necessary for
> function definitions, where the caller really needs to know the types of
> arguments to pass in.   At the moment that purpose is (I think adequately)
> served by def strings, triple quoted strings immediately following the function
> declaration.  When I do code reviews for Python developed here, if the
> argument names of a function do not hint at the type they should be and there
> is no def string then I insist that something be added.  Often what gets added
> is a def string that says something about what the function does and explains
> what argument types are expected.
> 
> -- Joseph S.
> 

I like having the option to add type hints to various things, including functions, but also classes, and the methods, and attributes of a class.   While I don't add them to every one of these every time, if I write a function that I expect to be used by someone else, I will annotate it.  Similarly, if I write a class that I expect to be instantiated or sub-classed as part of a library, I will annotate that as well, including any attributes that I expect to be used or changed.  

I haven't totally utilized the new type hinting yet, I am still often still documenting in the triple quoted strings using epytext type hinting, but that doesn't really handle things like "a list of strings", or even worse, " a dictionary that looks like dict("key1":1, "key2":"foobar") in a "standard" way (that I have found at least), or cases where an argument can be a string OR an int, or a list.  (I use the string/list option pretty regularly when I have functions that can handle one object, or multiple ones, and I've already used the * to break out something else).  I'm looking forward to finding the time to figure out how to best annotate those types of things.

And I have found that having these things well annotated does help my IDE (PyCharm) to keep me from making simple mistakes.

In the end, I figure that I don't see any real downside to the new type hinting, if I use it, great, if not, that's fine as well.  I would certainly not be supportive of making it required in order to compile though.