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Why are index() and count() only for mutable sequences?

Tim Peters tim_one at email.msn.com
Thu Jul 8 23:24:04 EDT 1999 
[Bob Alexander]
> There is no modification of the sequence performed by these functions
> -- it seems as though they could be available for all sequences. It
> would certainly be useful for tuples as well as lists (strings, too, for
> that matter, even though we have the more general string.find()).

I don't think there's a deep reason.  It was "just true" that immutable
objects (sequences or otherwise) didn't have methods when Python first came
out.  But when complex numbers were introduced, they came with a
.conjugate() method, and you can expect strings to grow methods too in 1.6
(Barry Warsaw has checked implementation code for that into the CVS tree,
disabled by default for now -- it's nice!).

As you say, strings have more flexible functions already, and there's reason
to suspect that Guido didn't expect anyone to use tuples of more than a few
elements each.

why-are-tabs-8-spaces<wink>-ly y'rs  - tim
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