python 17 lines · 5 steps

A reusable timing context manager in Python

Wrap any block in a with-statement to measure its wall-clock time and report it automatically.

Explained by highlit
Intermediate context-manager timing generators resource-cleanup
1import time
2from contextlib import contextmanager
3 
4 
5@contextmanager
6def timer(label="elapsed", logger=None):
7 start = time.perf_counter()
8 result = {"seconds": None}
9 try:
10 yield result
11 finally:
12 result["seconds"] = time.perf_counter() - start
13 message = f"{label}: {result['seconds'] * 1000:.2f}ms"
14 if logger is not None:
15 logger.info(message)
16 else:
17 print(message)
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1The @contextmanager decorator turns a single-yield generator into a full with-block protocol.
  2. 2Putting cleanup in a finally clause guarantees timing runs even when the wrapped code raises.
  3. 3Yielding a mutable object lets the caller read results the manager fills in after the block ends.

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