[Python-Dev] PEP 484: updates to Python 2.7 signature syntax (original) (raw)

Andrew Barnert abarnert at yahoo.com
Sat Mar 19 21:43:32 EDT 2016

On Mar 19, 2016, at 18:18, Guido van Rossum <guido at python.org> wrote:

Second, https://github.com/python/typing/issues/186. This builds on the previous syntax but deals with the other annoyance of long argument lists, this time in case you do care about the types. The proposal is to allow writing the arguments one per line with a type comment on each line. This has been implemented in PyCharm but not yet in mypy. Example: def gcd( a, # type: int b, # type: int ): # type: (...) -> int

This is a lot nicer than what you were originally discussing (at #1101? I forget...). Even more so given how trivial it will be to mechanically convert these to annotations if/when you switch an app to pure Python 3.

But one thing: in the PEP and the docs, I think it would be better to pick an example with longer parameter names. This example shows that even in the worst case it isn't that bad, but a better example would show that in the typical case it's actually pretty nice. (Also, I don't see why you wouldn't just use the "old" comment form for this example, since it all fits on one line and isn't at all confusing.)

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