question about for cycle

[George Sakkis]

On Sep 29, 10:34 am, "fdu.xia... at gmail.com" <fdu.xia... at gmail.com>
wrote:
> tokl... at gmail.com wrote:
>
>  > On 29 sep, 12:04, "fdu.xia... at gmail.com" <fdu.xia... at gmail.com> wrote:
>  >
>  >> for i in generator_a:  # the first "for" cycle
>  >>      for j in generator_b:
>  >>          if something_happen:
>  >>              # do something here ..., I want the outer cycle to break
>  >>              break
>  >
>  > Do you like this?
>  >
>  > generator_ab = ((x, y) for x in generator_a for y in generator_b)
>  > for i, j in generator_ab:
>  >     if condition:
>  >         # do something
>  >         break
>  >
>   In this case, the tuple generator_ab must be generated first.

It's not a tuple, it is a generator expression that can generate
tuples *lazily*.

> Sometime it maybe a waste to generate all possible combinations of i,j first.

It doesn't; read about generator expressions at http://www.python.org/dev/peps/pep-0289/

George