How to update a particular column of a row in a csv using python

I am having a csv file with the following contents

1,2,3,4
a,b,c,d
w,x,y,z

And i want to update this csv file contents to

1,2,3,4
a,b,c,开发者_运维问答d,k
w,x,y,z

Can someone please share Python code for this update process??

Using the csv library, we read in the data, convert it to a list of lists, append the k to the relevant list, then write it out again.

import csv

data = csv.reader(open("input.csv"))

l = list(data)    
l[1].append("k")

our_writer = csv.writer(open("output.csv", "wb"))

our_writer.writerows(l)

While the csv library isn't completely necessary for your toy case, it's often good to use the approach that scales well.

You don't need csv for such a simple case:

# sed '2s/$/,k/'
import fileinput
for lineno, line in enumerate(fileinput.input(inplace=True), start=1):
    if lineno == 2:
       line = line.rstrip('\n') + ",k\n"
    print line,

Example:

$ python update_2nd_line.py data_to_update.csv

It updates data_to_update.csv file inplace.