[Python-Dev] AC Derby and accepting None for optional positional arguments (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Thu Jan 16 09:31:17 CET 2014

16.01.14 08:05, Guido van Rossum написав(ла):

In this specific case it's clear to me that the special-casing of negative count is intentional -- presumably it emulates sequence repetition, where e.g. 'a'*-1 == ''.

In this specific case it's contrary to sequence repetition. Because repeat('a', -1) repeats 'a' forever. This is a point of Vajrasky's issue [1].

But not accepting None is laziness -- accepting either a number or None requires much more effort, if you need to have the number as a C integer. I'm not sure how AC could make this any easier, unless you want to special-case maxint or -maxint-1.

getattr(foo, 'bar', None) is not the same as getattr(foo, 'bar'). So None can't be used as universal default value.

[1] http://bugs.python.org/issue19145

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