== Fixing Python's string _.join()_

The thing that has always irritated me about string _.join()_ is that it
doesn't stringify its arguments; if one of the things in the sequence to
be joined isn't a string, _.join()_ doesn't call _str()_ on it, it just
pukes. This is periodically annoying and inconvenient.

It recently occurred to me that this can be fixed, like so:

 class StrifyingStr(str):
   def join(self, seq):
     s2 = [str(x) for x in seq]
     return super(StrifyingStr, self).join(s2)

 def str_join(js, seq):
   return StrifyingStr(js).join(seq)

(A similar version for Unicode strings is left as an exercise for
the reader.)

You might think that a generator expression would be more efficient
than a list comprehension here; in fact, that's what my first version
used. Then I actually timed it, and found out that regardless of whether
or not _.join()_ was passed a list or an iterator, and for sizes of
the list (or iterator) from 10 elements to 10,000, doing the list
comprehension was slightly faster.

Now that I have this I can think of a number of places where I may wind
up using it, which kind of makes me wish I'd scratched this irritation
before now.