get how much time python subprocess spends

Question

I\'d like to time how long does the subprocess take. I tried to use

start = time.time()
subprocess.call(\'....\')
elapsed = (time.time() - start)

Answer 1

It took me a little while to implement Roland's solution due to the annoyingness of passing around python code as strings, so I thought I'd share a working example.

This script times an external program in the working directory, and redirects its standard output and standard error to files.

from timeit import timeit

reps = 500
stdout = open("add_numbers_outputs.log", 'w')
stderr = open("add_numbers_errors.log", 'w')
external_command = "./add_numbers"
parameter = str(1000000) # one million

call_arguments = """[
        '%s',
        '%s'], # pass additional parameters by adding elements to this list
        stdout=stdout,
        stderr=stderr
""" % (external_command, parameter)

print "Timing external command "+external_command+" with parameter "+parameter

time_taken = timeit(stmt = "subprocess.call(%s)" % call_arguments,
        setup = """import subprocess;
stdout = open("add_numbers_outputs.log", 'w');
stderr = open("add_numbers_errors.log", 'w')
""",
        number = reps) / reps

print "Average time taken for %s repetitions: %f seconds" % (reps, time_taken)