i = 0
seq = ['one', 'two', 'three']
for element in seq:
  print i, seq[i]
  i += 1
#0 one
#1 two
#2 three
print '============'
seq = ['one', 'two', 'three']
for i, element in enumerate(seq):
  print i, seq[i]
print '============'
for i,j in enumerate('abc'):
  print i,j
#0 a
#1 b
#2 c
print '============'
def _treatment(pos, element):
  return '%d: %s' %(pos, element)
seq = ['one', 'two', 'three']
print [_treatment(i, e1) for i, e1 in enumerate(seq)]

0 one
1 two
2 three
============
0 one
1 two
2 three
============
0 a
1 b
2 c
============
['0: one', '1: two', '2: three']