Appending two CSV files column-wise

Question

Suppose I have two CSV files called A and B in Python.

A\'s head looks like:

 headerName         


        

Answer 1

If you get two file handles for the same file - one in 'read' mode, one in 'update' mode (r+b), the same strategy should work.

from itertools import izip
import csv
with open('A','rb') as f1, open('B','rb') as f2, open('A','r+b') as w:
    writer = csv.writer(w)
    for r1,r2 in izip(csv.reader(f1),csv.reader(f2)):
        writer.writerow(r1+r2)

When possible I'd recommend against this kind of thing and just explicitly write to a third file.