Line and char counter

lc.py

#!/usr/bin/env python
"""lc: a linecounter. reads stdin and prints advancement in numbers of chars/lines

Usage:
   lc -l INTERVAL [--thru]
   lc -c INTERVAL [--thru]

Options:
   -l INTERVAL  output a message every INTERVAL lines [default: 100]
   -c INTERVAL  output a message every INTERVAL characters [default: 100]
   -t --thru    passthrough data on stdout and display progress on stderr
"""

import docopt
import sys

MESG_FORMAT = "Output {} lines"

def lc_line(fd, count, thru):
  linenum = 0
  if thru:
    o = sys.stderr
  else:
    o = sys.stdout
  while True:
    line = fd.readline()
    if thru:
      print(line, end='')
    if not line:
      break
    linenum += 1
    if linenum % count == 0:
      print(MESG_FORMAT.format(linenum), file=o)
  print(f"Finished with {linenum} lines", file=o)

def lc_char(fd, count, thru):
  charnum = 0
  step = count
  total_chars = 0
  if thru:
    o = sys.stderr
  else:
    o = sys.stdout
  while True:
    readstuff = fd.read(step)
    if thru:
      print(readstuff, end='')
    total_chars += len(readstuff)
    if len(readstuff) < step:
      print(f"Nearing end with {total_chars} characters", file=o)
    elif not len(readstuff):
      break
    else:
      print(f"Read {total_chars} characters", file=o)
  print(f"Finished with {total_chars} characters", file=o)

if __name__ == '__main__':
  args = docopt.docopt(__doc__)
  if args['-l']:
    lc_line(sys.stdin, int(args['-l']), True if args['--thru'] else False)
  elif args['-c']:
    lc_char(sys.stdin, int(args['-c']), True if args['--thru'] else False)
  else:
    raise RuntimeError("Wrong arguments")