replace string inside double quotes

[nilamo]

import csv

new_rows_list = []

# Read File
f1 = open('in_file', 'r')
reader = csv.reader(f1, delimiter=',')
for row in reader:
    new_row = ([col.replace(',', '^') for col in row])
    new_rows_list.append(new_row)


# Write File
f2 = open('out_file', 'w')
writer = csv.writer(f2)
writer.writerows(new_rows_list)
f2.close()
f1.close()

Don't store the whole file in memory, just work on it line-by-line:

import csv

with open("in_file", "r", newline="") as f1:
    reader = csv.reader(f1, delimiter=",")
    with open("out_file", "w", newline="") as f2:
        writer = csv.writer(f2)
        for row in reader:
            new_row = [col.replace(",", "^") for col in row]
            writer.writerow(new_row)