Using CSV module in Python to replace zeros

Here's a short script that will read a CSV file, convert any numbers to floats and then write it back to the same file again.

import csv
import sys

# These indices won't be converted
dont_touch = [0]
def convert(index, value):
    if not index in dont_touch:
         try:
              return float(value)
         except ValueError:
              # Not parseable as a number
              pass
    return value

table = []
with open(sys.argv[1]) as f:
    for row in csv.reader(f, delimiter=","):
        for i in range(len(row)):
            row[i] = convert(i, row[i])
                table.append(row)

with open(sys.argv[1], "w") as f:
    writer = csv.writer(f, delimiter=",")
        writer.writerows(table)

If you have any columns that should not be converted, specify their indices in the dont_touch array.

If you want them to have two trailing zeroes you can play around with format strings instead:

return "{:.02f}".format(float(value))

You can format the 0s and then write them out, you may want to look into the appropriate quoting for your csv (e.g. you may need quoting=csv.QUOTE_NONE in your writer object):

reader = csv.reader(fr)
writer = csv.writer(fw)
for row in reader:
    writer.writerow([f if f != '0' else '{:0.2f}'.format(0) for f in row])