Count lines in text-file (works w/ Nautilus Script)

Count_the_lines.py

#!/usr/bin/python -tt

import sys
import os
import subprocess

def main(filenames):
  for filename in filenames:
    fcmd = "file -bi '"+filename+"'"
    f = os.popen(fcmd,"r")
    if f.read().startswith("text"):
      with open(filename) as f:
        for i, l in enumerate(f):
          pass
      i = i + 1
      i = str(i)
      subprocess.call(("notify-send -t 7000 -i 'format-text-bold-symbolic' 'Python Line Counter' '"+filename+" has "+i+" lines.'"), shell=True)
    else:
      subprocess.call(("notify-send -t 7000 -i error 'Python Line Counter' '"+filename+" isn not a textfile!!'"), shell=True)
      sys.exit(1)




if __name__ == "__main__":
  args = sys.argv[1:]
  if len(args) == 0:
    subprocess.call(("notify-send -t 3000 'Python Line Counter' 'Error: Call this as a Nautilus Script, or \'Count_the_lines.py myfile.txt\''"), shell=True)
    sys.exit(1)
  else:
    main(args)