[issue19145] Inconsistent behaviour in itertools.repeat when using negative times

[Larry Hastings]

Larry Hastings added the comment:

This problem been independently rediscovered by people converting
code to Argument Clinic.  A Python signature can't express these
semantics, where a parameter behaves differently depending on
whether it's passed in by keyword or by reference.  So Argument
Clinic can't either.  I think it would be best if itertools.repeat
behaved like a pure Python function--that is, that it behaved
the same whether "times" was passed in by position or by keyword.

What's I find curious: the documentation is wildly out of sync with the implementation.  It says:

    itertools.repeat(object[, times])
    ....
    def repeat(object, times=None):
        ....

    http://docs.python.org/3.4/library/itertools.html#itertools.repeat

But repeat() doesn't support passing in None for the times parameter,
if indeed it ever has.


I see two possible choices here.

1) Honor the existing behavior.  Change the signature to simply

   def repeat(object, times=-1):

   and document it that way.

2) Honor the documentation.  Change the implementation to

   def repeat(object, times=None):

   This change could break code.  So we'd have to go through a
   deprecation cycle.  Breaking "times=-1" without a deprecation
   cycle is simply not viable at this point.

I could live with either.

----------
nosy: +larry

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