Python parse csv file - replace commas with colons

The answer is easier than you think. You just need to set the delimiter for csv.writer:

import csv

row = #your data

with open("temp.csv", mode="rU") as infile:
    reader = csv.reader(infile, dialect="excel")    
    with open("temp2.txt", mode="w") as outfile:
        writer = csv.writer(outfile, delimiter=':')
        writer.writerows(rows)

You're line trying to replace , with : wasn't going to do anything because the row had already been processed by csv.reader.

If you are looking to read a csv with comma delimiter and write it in another file with semicolon delimiters. I think a more straightforward way would be:

reader = csv.reader(open("input.csv", "r"), delimiter=',')
writer = csv.writer(open("output.csv", 'w'), delimiter=';')
writer.writerows(reader)

I find this example much easier to understand than with the with open(...). Also if you work with file using comma and semicolon as delimiters. You can use the Sniffer of the csv file to detect which delimiter is used before reading the file (example in the link).

Also if you want to rewrite in the same file, check this stackoverflow answer.

I will build my answer on @Sylhare's answer. In python3, the 'U' mode is deprecated. So, the following solution worked for me:

import csv

reader = csv.reader(open("input.csv", newline=None), delimiter=',')
writer = csv.writer(open("output.csv", 'w'), delimiter=':')
writer.writerows(reader)