profileit

Timers, like the timeit module, or a timing decorator can help to find candidates for optimisation. Proper profiling is better, but it can sometimes be difficult to isolate the specific area in order to run the cProfile module. A decorator can help.

Recently, I was trying to speed up a slow running web response. Certain requests, fetching certain data, were much slower, and it looked tricky to set up an appropriate harness and set of stubs to be able to run python -m cProfile somefile.py.

Enter the profileit decorator, which outputs results in the same manner as teh cProfile module.

import cProfile
import pstats


def profileit(limit=30):

    def inner_profileit(func):
        def wrapper(*args, **kwargs):
            prof = cProfile.Profile()
            retval = prof.runcall(func, *args, **kwargs)
            prof.create_stats()
            pstats.Stats(prof).sort_stats('cumtime').print_stats(limit)
            return retval
        return wrapper
    return inner_profileit

This decorator is particularly useful for profiling user-actuated functions in longer running applications such as a desktop GUI or web application.

As a pleasant side-effect, because it shows a list of (some of) the functions it can be a quick way to get an overview of the path a request may take through an unfamiliar application before diving in and reading the code or stepping through with a debugger.