Some thougts on cartesian products

[Bryan Olson]

Christoph Zwerschke wrote:
> In Python, it is possible to multiply a string with a number:
> 
>  >>> "hello"*3
> 'hellohellohello'

Which is really useful.

> However, you can't multiply a string with another string:
> 
>  >>> 'hello'*'world'
> Traceback (most recent call last):
>   File "<interactive input>", line 1, in ?
> TypeError: can't multiply sequence by non-int
>
> Sometimes I was missing such a feature.
> What I expect as the result is the "cartesian product" of the strings.

There's no such thing; you'd have to define it first. Are duplicates
significant? Order?

What you seem to want is easy enough:

   [a + b for a in 'hello' for b in 'world']

[...]
> Cartesian products may be generally interesting for iterables:

And maybe you want the result to be a generator:

     (a + b for a in 'hello' for b in 'world')


New language features should be widely useful, and difficult or
awkward to code in Python as it is. All-combinations-of-sequences
is trivial to code and rarely needed.


-- 
--Bryan