Logging Execution Time in Python

Decorators in Python allow us to run arbitrary code before and after a function or class instantiation is called. One super useful application of this is logging the time it takes for a function to run. Here is a snippet I often use for just that:

from time import time


def print_execution_time(function):
    def timed(*args, **kw):
        time_start = time()
        return_value = function(*args, **kw)
        time_end = time()

        execution_time = time_end - time_start

        arguments = ", ".join(
            [str(arg) for arg in args] + [f"{k}={kw[k]}" for k in kw]
        )
        print(
            f"{function.__name__}({arguments}) took {execution_time * 1000:.4f} ms"
        )

        return return_value

    return timed


@print_execution_time
def repeat(number, n_repeats=30000):
    return [number for number in range(30000)]


repeat(9)
repeat(20, 40000)
repeat(1, n_repeats=4000)

This will print the execution time in milliseconds and the name of the function run with its arguments:

1.001596450805664 ms repeat(9)
1.0008811950683594 ms repeat(20, 40000)
1.0001659393310547 ms repeat(1, n_repeats=4000)