Q:

Python: search and print lines in a file by increments of 2

I am new so I hope this isn't redundant.  Lets say I have an input file named "mccell" that looks like 
     Initial Molecules:                 47
     Initial Molecules:                  1
       1          47
       1           1
       2          48
       2           0
       3          48
       3           0
       4          48
       4           0
       5          48
       5           0
       6          48
       6           0
       7          48
       7           0
       8          48
       8           0
       9          48
       9           0

I am trying to figure out how I would go about printing specific lines in increments that I specify.  For example, how would I start at the line "Initial Molecule" and print ONLY the lines that are in increments of two after.  To illustrate what I am describing what I want the code to do:
    Initial Molecules:                 47
    1          47
    2          48
    3          48
    4          48
    5          48
    6          48
    7          48
    8          48
    9           48

I have tried the readlines() function, but to no avail as I can only print the entire file.  This is the incorrect code that I have:
    fo = open("mccell")
    lines = fo.readlines()
    print lines

Any help or tips would be appreciated.  Thanks! 

A:

You could use the range method to do the trick. 
fo = open("mccell")
lines = fo.readlines()
print lines

Iterate over the lines, since lines are stored internally as a list object in python and you could use range ranging from 0 to len(lines) by 2 steps
for i in range(0, len(lines), 2):
    print lines[i]

