How to transpose a dataset in a csv file?

Question

For example, i would like to transform:

Name,Time,Score
Dan,68,20
Suse,42,40
Tracy,50,38

Into:

Name,Dan,Suse,Tracy
Time,68,         


        

Answer 1

If the whole file contents fits into memory, you can use

import csv
from itertools import izip
a = izip(*csv.reader(open("input.csv", "rb")))
csv.writer(open("output.csv", "wb")).writerows(a)

You can basically think of zip() and izip() as transpose operations:

a = [(1, 2, 3),
     (4, 5, 6),
     (7, 8, 9)]
zip(*a)
# [(1, 4, 7),
#  (2, 5, 8),
#  (3, 6, 9)]

izip() avoids the immediate copying of the data, but will basically do the same.