Replace data in csv file using python

Question

This is the new input file format. I need to automate the process of replacing the content of one column in a .csv file with the use of python. I can also open the .csv file using Notepad and replace the content of the column but the file is very huge and it is taking a long time.

Name                          ID                                                class  Num
"kanika",""University ISD_po.log";" University     /projects/asd/new/high/sde"","MBA","12"
"Ambika",""University ISD_po.log";" University     /projects/asd/new/high/sde"","MS","13"

In the above, I need to replace the content of ID column. ID column is very inconsistent as it has big spaces and symbols like(; , /) in the content.The new content in the ID column should be "input".

This Id column is enclosed with 2 double quotes and has some extra spaces as well. Whereas other columns have only 1 double quote.

Is there any way to do it in python?

Answer 1

You could use the csv module in Python to achieve this.

csv.reader will return each row as a list of strings. You could then use csv.writer to stream each row and modify the ID column at this point, this will create a new file though.

So:

import csv
reader = csv.reader(open('file.csv', 'rb'))
writer = csv.writer(open('outfile.csv','wb'))
for row in reader:
    writer.writerow([row[0], "input", row[2], row[3]])

Answer 2

Read the .csv line-by-line, split on ,, and replace the second column with "input". Write it out (to a different file) as you go:

f = open('mycsv.csv','rb')
fo = open('out.csv','wb')

# go through each line of the file
for line in f:
    bits = line.split(',')
    # change second column
    bits[1] = '"input"'
    # join it back together and write it out
    fo.write( ','.join(bits) )

f.close()
fo.close()

Then you can rename it to replace the original file if you like.