How can I, in python, iterate over multiple 2d lists at once, cleanly?

Question

If I\'m making a simple grid based game, for example, I might have a few 2d lists. One might be for terrain, another might be for objects, etc. Unfortunately, when I need to ite

Answer 1

Generator expressions and izip from itertools module will do very nicely here:

from itertools import izip
for a, b in (pair for (aline, bline) in izip(alist, blist) 
             for pair in izip(aline, bline)):
    if a.isWhatever:
        b.doSomething()

The line in for statement above means:

• take each line from combined grids alist and blist and make a tuple from them (aline, bline)
• now combine these lists with izip again and take each element from them (pair).

This method has two advantages:

• there are no indices used anywhere
• you don't have to create lists with zip and use more efficient generators with izip instead.