X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=stopwatch.py;h=fa4f2b52f54998bb029f7e14433e5451abd67812;hb=e8fbbb7306430478dec55d2c963eed116d8330cc;hp=d54af8792d28eef4025c150cb1920fbd2113efee;hpb=1574e8a3a8982fab9278ad534f9427d464e4bffb;p=python_utils.git

diff --git a/stopwatch.py b/stopwatch.py
index d54af87..fa4f2b5 100644
--- a/stopwatch.py
+++ b/stopwatch.py
@@ -1,27 +1,36 @@
 #!/usr/bin/env python3
 
+"""A simple stopwatch decorator / context for timing things."""
+
 import time
-from typing import Callable
+from typing import Callable, Optional
 
 
 class Timer(object):
     """
-    with timer.Timer() as t:
-        do_the_thing()
+    A stopwatch to time how long something takes (walltime).
+
+    e.g.
 
-    walltime = t()
-    print(f'That took {walltime}s.')
+        with stopwatch.Timer() as t:
+            do_the_thing()
+
+        walltime = t()
+        print(f'That took {walltime} seconds.')
     """
 
     def __init__(self) -> None:
-        self.start = None
-        self.end = None
+        self.start = 0.0
+        self.end = 0.0
 
     def __enter__(self) -> Callable[[], float]:
+        """Returns a functor that, when called, returns the walltime of the
+        operation in seconds.
+        """
         self.start = time.perf_counter()
         self.end = 0.0
         return lambda: self.end - self.start
 
-    def __exit__(self, *args) -> bool:
+    def __exit__(self, *args) -> Optional[bool]:
         self.end = time.perf_counter()
-        return True
+        return None  # don't suppress exceptions