ROSALIND RNA

Given: A DNA string t having length at most 1000 nt.
Return: The transcribed RNA string of t.

import sys
import re

def main():
 if len(sys.argv) > 1:
  print re.sub(r'T', r'U', sys.argv[1])
 else:
  print 'Enter your sequence!'

if __name__ == '__main__':
 main()