XORing long strings opimization?

[rm]

Skip Montanaro <skip at pobox.com> wrote in message news:<mailman.448.1067985794.702.python-list at python.org>...
> Noen>   alist = [chr(x ^ y) for x in ord1 for y in ord2]
> 
>     Noen> This creates a way too big list... Im not familiar with two for
>     Noen> loops in one, so I cant see whats wrong :(
> 
> Try:
> 
>     alist = [chr(x ^ y) for (x, y) in zip(ord1, ord2)]
> 
> Your listcomp nests two for loops.  You need to iterate over both ord1 and
> ord2 at the same time.
> 
> Skip

this could work as well:

import itertools

alist = [ chr(x^y) for x,y in itertools.izip( itertools.imap(ord,a) ,
itertools.imap(ord,b)) ]

if I'm not mistaken this will pull out 1 character at a time, maybe
not fastest method, but you won't have multiple copies of the list
(original or transformed), and when you're comparing big files this
might be advisable

rm