minimal statusbar watcher

py_watch.py

import sys
import time

def reprint(msg):
  """Print msg from beginning of last line."""
  sys.stdout.write('\r')
  sys.stdout.write(str(msg))
  sys.stdout.flush()
  
def watch(fn, update=0.25):
  """Print the result of `fn` every `update` to last line of stdout."""
  result = fn()
  while result:
    reprint(result)
    time.sleep(update)
    result = fn()
    
if __name__ == '__main__':
  # Example with datetime.datetime.now()
  import signal
  import datetime
  # on catching SIGINT write a newline and exit
  signal.signal(signal.SIGINT, lambda *_: print() or sys.exit(0))
  # run watcher with a .5 s update interval
  watch(datetime.datetime.now, update=.5)