[Python-Dev] Inconsistent string.replace() behavior

[Tim Peters]

[Guido]
> HMMMMMM!  In Python 1.5, a count of zero always replaces all
> occurrences, both using string and using strop.  In 2.0 and later,
> strop's replace(..., 0) still replaces all, but string's replaces
> none.  The replace() method of strings and unicode objects agrees with
> string.py.
>
> I think this change was made in the sake of ease of documenting the
> behavior: special-casing the count of zero is unexpected.

Yes, -1 == infinity is much clearer <wink>.

> I very vaguely recall that it was discussed on this list.
>
> So this suggests that test_string is correct, and string.replace()
> (and the methods) shouldn't be "fixed"!

I didn't change their behavior wrt replace()'s interpretation of count, but
to repair an unrelated bug (bogus MemoryError for an empty-string *result*)
that happened to appear in both copies of mymemreplace sitting in the code
base (one in stringobject.c, another but out-of-synch one in stropmodule.c).
That's how stropmodule got sucked into this:  to fix the gross null-string
result bug common to both.

> But since we're not really supporting strop any more, I think that
> strop shouldn't be changed either.  So we'll have to live with the
> difference -- sorry!

OK, I've restored the 0 == infinity semantics to strop.replace() and
test_strop.py, but have not backed out the null-string result fix, nor the
pain to make the mymemreplace clones identical again.