Dabeaz

As a followup to my last blog post on timings, I present the following function which works as both a decorator and a context manager.

# timethis.py
import time
from contextlib import contextmanager

def timethis(what):
    @contextmanager
    def benchmark():
        start = time.time()
        yield
        end = time.time()
        print("%s : %0.3f seconds" % (what, end-start))
    if hasattr(what,"__call__"):
        def timed(*args,**kwargs):
            with benchmark():
                return what(*args,**kwargs)
        return timed
    else:
        return benchmark()

Here is a short demonstration of how it works:

# Usage as a context manager
with timethis("iterate by lines (UTF-8)"):
     for line in open("biglog.txt",encoding='utf-8'):
          pass

# Usage as a decorator
@timethis
def iterate_by_lines_latin_1():
    for line in open("biglog.txt",encoding='latin-1'):
        pass

iterate_by_lines_latin_1()

If you run it, you'll get output like this:

bash % python3 timethis.py
iterate by lines (UTF-8) : 3.762 seconds
<function iterate_by_lines_latin_1 at 0x100537958> : 3.513 seconds

Naturally, this bit of code would be a good thing to bring into your next code review just to make sure people are actually paying attention.

posted by Dave  # 6:12 PM