stopwatch.py

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