How can I tell when a string is in fact a number?

[Fredrik Lundh]

Joshua wrote:
> Why use re at all?

maybe because it's designed for this very purpose, and
is faster than any other solution?

> def isanum(str):
>     import string
>     return reduce(lambda x, y: x and y in string.digits, str, str != "")

...while map/filter/reduce on lambda expressions are
known to be slow.

> why-does-everyone-always-try-to-present-a-solution-to-
> something-other-than-the-original-problem'ly yrs,

really?  I probably have a really lousy newsfeed, because
I couldn't find a single off-topic reply...

</F>