Question

The following appears in my Python 2.6 code:

for src, dst in ([s,d] for s in universe for d in universe if s != d):

Can I do much better? What I particularly don’t like is that I’m in effect specifying the same pair twice, once for the for loop and again for the generator expression. I’m uncertain whether I’d prefer:

for src, dst in itertools.product(universe, universe):
    if src != dst:

Is there a way to express this loop concisely?

universe happens to be a list, if it makes any difference. Order of iteration doesn’t matter.

Answer 1

You could use simple nested for-loops:

for src in universe:
   for dst in universe:
      if src == dst:
         continue
      ...

I’d say this is the most easy to read syntax in this case.