Time function from python script from the command line

Question

I'd like to time functions from scripts, preferably not modifying said scripts (i.e adding timer decorators, or functions).

Answer 1

From the command line, run timeit module as a script passing the additional setup argument (-s). The setup should import the function you wish to time from your script.

Finally, remember to add the call to that function.

WARNING: setup will run once, importing your script. Import runs all "unprotected code", so remember to use the if __name__ == "__main__" convention to split function/object declarations from actual execution.

Imagine the following script.py

import time

print('This will be run on import')

def fun():
    pass

def very_complex_function_that_takes_an_hour_to_run():
    time.sleep(3600)

if __name__ == '__main__':
    print("Nothing beyond the if condition will be run on import")
    very_complex_function_that_takes_an_hour_to_run()

Let's time fun, running it 100 times.

$ python -m timeit -s 'from test import fun' -n 100 'fun()'

Output

This will be run on import
100 loops, best of 5: 66.6 nsec per loop