[Python-Dev] PEP 457: Syntax For Positional-Only Parameters (original) (raw)

Larry Hastings larry at hastings.org
Wed Oct 9 19:05:36 CEST 2013

On 10/09/2013 06:48 PM, Terry Reedy wrote:

On 10/9/2013 9:51 AM, Larry Hastings wrote:

range() in PyPy accepts keyword parameters, and in fact this works:

range(9, step=2) That's way illegal in CPython. But Georg's point is that it does not have to be illegal in CPython. Range, in particular, does not have to be blazingly fast since it wraps loops rather than being in loops. I quite agree that it would be better to fix most functions.

First, if you're proposing to change the signature of range()... well, good luck. Any proposals I made like that got shot down almost immediately. I /think/ Guido said somewhere "range isn't changing.
deal with it.", though I admit I don't have a reference for that handy.

Also, if you're suggesting "change the semantics of builtins to get rid of positional-only parameters", I've got a different example for you: the dict constructor, which /must/ accept a single optional positional-only parameter. The only way to simulate that in Python code is with *args, but now introspection on that function will be misleading, because the dict constructor doesn't accept more than one positional-only argument.

And, as Georg suggests, these niggling inconsistencies are the hobgoblins of my small mind.

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