How to enumerate a list of non-string objects in Python?

Question

There is a nice class Enum from enum, but it only works for strings. I'm currently using:

    for index in range(len(objects)):
        # do something with index and objects[index]

I guess it's not the optimal solution due to the premature use of len. How is it possible to do it more efficiently?

Answer 1

Here is the pythonic way to write this loop:

for index, obj in enumerate(objects):
  # Use index, obj.

enumerate works on any sequence regardless of the types of its elements. It is a builtin function.

Edit:

After running some timeit tests using Python 2.5, I found enumerate to be slightly slower:

>>> timeit.Timer('for i in xrange(len(seq)): x = i + seq[i]', 'seq = range(100)').timeit()
10.322299003601074
>>> timeit.Timer('for i, e in enumerate(seq): x = i + e', 'seq = range(100)').timeit()
11.850601196289062