stopwatch.py

   1 #!/usr/bin/env python3
   2
   3 import time
   4 from typing import Callable, Optional
   5
   6
   7 class Timer(object):
   8     """
   9     A stopwatch to time how long something takes (walltime).
  10
  11     e.g.
  12
  13         with timer.Timer() as t:
  14             do_the_thing()
  15
  16         walltime = t()
  17         print(f'That took {walltime} seconds.')
  18     """
  19
  20     def __init__(self) -> None:
  21         self.start = 0.0
  22         self.end = 0.0
  23
  24     def __enter__(self) -> Callable[[], float]:
  25         """Returns a functor that, when called, returns the walltime of the
  26         operation in seconds.
  27         """
  28         self.start = time.perf_counter()
  29         self.end = 0.0
  30         return lambda: self.end - self.start
  31
  32     def __exit__(self, *args) -> Optional[bool]:
  33         self.end = time.perf_counter()
  34         return None  # don't suppress exceptions