How to measure elapsed time in Python?

Question

What I want is to start counting time somewhere in my code and then get the passed time, to measure the time it took to execute few function. I think I'm using the timeit module wrong, but the docs are just confusing for me.

import timeit  start = timeit.timeit() print("hello") end = timeit.timeit() print(end - start) 

Answer 1

If you just want to measure the elapsed wall-clock time between two points, you could use time.time():

import time  start = time.time() print("hello") end = time.time() print(end - start) 

This gives the execution time in seconds.

Another option since 3.3 might be to use perf_counter or process_time, depending on your requirements. Before 3.3 it was recommended to use time.clock (thanks Amber). However, it is currently deprecated:

On Unix, return the current processor time as a floating point number expressed in seconds. The precision, and in fact the very definition of the meaning of “processor time”, depends on that of the C function of the same name.

On Windows, this function returns wall-clock seconds elapsed since the first call to this function, as a floating point number, based on the Win32 function QueryPerformanceCounter(). The resolution is typically better than one microsecond.

Deprecated since version 3.3: The behaviour of this function depends on the platform: use perf_counter() or process_time() instead, depending on your requirements, to have a well defined behaviour.

Answer 2

Use timeit.default_timer instead of timeit.timeit. The former provides the best clock available on your platform and version of Python automatically:

from timeit import default_timer as timer  start = timer() # ... end = timer() print(end - start) # Time in seconds, e.g. 5.38091952400282 

timeit.default_timer is assigned to time.time() or time.clock() depending on OS. On Python 3.3+ default_timer is time.perf_counter() on all platforms. See Python - time.clock() vs. time.time() - accuracy?

See also:

• Optimizing code
• How to optimize for speed