How do I measure elapsed time in Python?

Use time.time() to measure the elapsed wall-clock time between two points:

import time

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

This gives the execution time in seconds.

Another option since Python 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.