What's the easiest way to iterate on a file's lines, keeping a counter?

Question

What's the cleanest code that iterates on the lines of a text file, while simultaniously increamenting a counter?

I understand that with multiple assignment, there's a cleaner syntax than

i = 0
for line in f:
    ...
    ++i

Answer 1

for i, line in enumerate(f):
  print i, line

As seen here: http://docs.python.org/library/functions.html#enumerate