Question

I have a list and it contains lists. The inner lists are may be empty. This is the structure:

[[],[a,b],[],[c],[d]]

My code:

for inner in list:
   for char in inner:
      print char           # I want to add indexes of inner lists here

Output is:

abcd

I want the output to be:

2a2b4c5d

The numbers are indexes of inner lists. Is there quick way to do this?

Answer 1

please note that you should not use list as a variable name, since it shadows the built-in list type.

>>> lst = [[],['a','b'],[],['c'],['d']]
>>> for idx, inner in enumerate(lst):
      for char in inner:
        print idx, char


1 a
1 b
3 c
4 d

you see that enumerate() counts zero-based. you can specify a second argument as start though, to match your one-based expected output:

>>> for idx, inner in enumerate(lst, 1):
    for char in inner:
        print idx, char


2 a
2 b
4 c
5 d

but only do that if neccessary, python counts 0-based by convention.