import sys
import csv

tabin = csv.reader(sys.stdin, dialect=csv.excel_tab)
commaout = csv.writer(sys.stdout, dialect=csv.excel)
for row in tabin:
  commaout.writerow(row)

import sys
import csv

commain = csv.reader(sys.stdin, dialect=csv.excel)
tabout = csv.writer(sys.stdout, dialect=csv.excel_tab)
for row in commain:
  tabout.writerow(row)

run this with the following syntax:

python script.py < input.file > output.file

Adopted and adjusted from StackOverFlow