shuffle population labels in a csv file

shuffler.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from random import shuffle

# create a list of all labels - NOTE that i've used 2 here because we have
# 2 individuals in pop A and 2 in pop B
label_list = ["population-A"] * 2 + ["population-B"] * 2
# do something 100 times
for i in xrange(100):
    # you can remove this
    print "Draw # {}\n".format(i)
    # shuffle the list in place (meaning there is no return - the list is literately shuffled)
    shuffle(label_list)
    # open a csv file (no header)
    with open("test.csv", "rU") as infile:
        # for each line in the file
        for line_number, line in enumerate(infile):
            # strip the newline at the end and split the line on commas
            line_split = line.strip().split(",")
            # replace the 2nd item in the list with a selection from the shuffled labels
            line_split[1] = label_list[line_number]
            # glue all that stuff back together
            new_line = ",".join(line_split)
            # print it out (this should be replaced by writing to an output file
            print new_line
    print "\n"

test.csv

Expected output is something like the following:

Draw # 0

individual-1,population-A,00,11,10,01,11,00
individual-2,population-A,00,10,10,01,11,00
individual-3,population-B,11,10,10,01,11,00
individual-4,population-B,11,10,10,01,11,00

Draw # 1

individual-1,population-A,00,11,10,01,11,00
individual-2,population-A,00,10,10,01,11,00
individual-3,population-B,11,10,10,01,11,00
individual-4,population-B,11,10,10,01,11,00

Draw # 2

individual-1,population-A,00,11,10,01,11,00
individual-2,population-B,00,10,10,01,11,00
individual-3,population-A,11,10,10,01,11,00
individual-4,population-B,11,10,10,01,11,00