Something

>>> f1 = open("data")
>>> f1
<open file 'data', mode 'r' at 0xb7b803c8>
>>> for line in f1:
...     print line,
...
a:b:c
c:d:e
#1:2:3
>>> for line in f1:
...     if not line.startswith('#'):
...             print line.split(":")
...
>>> f1
<open file 'data', mode 'r' at 0xb7b803c8>
>>> f1 = open("data")
>>> for line in f1:
...      if not line.startswith('#'):
...              print line.split(":")
...
['a', 'b', 'c\n']
['c', 'd', 'e\n']