Get time of execution of a block of code in Python 2.7

问题

I would like to measure the time elapsed to evaluate a block of code in a Python program, possibly separating between user cpu time, system cpu time and elapsed time.

I know the timeit module, but I have many self-written functions and it is not very easy to pass them in the setup process.

I would rather have something that could be used like:

#up to here I have done something....
start_counting() #or whatever command used to mark that I want to measure
                   #the time elapsed in the next rows
# code I want to evaluate
user,system,elapsed = stop_counting() #or whatever command says:
                                      #stop the timer and return the times

The user and system CPU times are not essential (though I would like to measure them), but for the elapsed time I would like to be able to do something like this, rather than using complicated commands or modules.

回答1:

To get the elapsed time in seconds, you can use timeit.default_timer():

import timeit
start_time = timeit.default_timer()
# code you want to evaluate
elapsed = timeit.default_timer() - start_time

timeit.default_timer() is used instead of time.time() or time.clock() because it will choose the timing function that has the higher resolution for any platform.

回答2:

I always use a decorator to do some extra work for a existing function, including to get the execution time. It is pythonic and simple.

import time

def time_usage(func):
    def wrapper(*args, **kwargs):
        beg_ts = time.time()
        retval = func(*args, **kwargs)
        end_ts = time.time()
        print("elapsed time: %f" % (end_ts - beg_ts))
        return retval
    return wrapper

@time_usage
def test():
    for i in xrange(0, 10000):
        pass

if __name__ == "__main__":
    test()

回答3:

I found myself solving this problem again and again, so I finally created a library for it. Install with pip install timer_cm. Then:

from time import sleep
from timer_cm import Timer

with Timer('Long task') as timer:
    with timer.child('First step'):
        sleep(1)
    for _ in range(5):
        with timer.child('Baby steps'):
            sleep(.5)

Output:

Long task: 3.520s
  Baby steps: 2.518s (71%)
  First step: 1.001s (28%)

回答4:

You can achieve this through the Context Manager, for example:

from contextlib import contextmanager
import time
import logging
@contextmanager
def _log_time_usage(prefix=""):
    '''log the time usage in a code block
    prefix: the prefix text to show
    '''
    start = time.time()
    try:
        yield
    finally:
        end = time.time()
        elapsed_seconds = float("%.2f" % (end - start))
        logging.debug('%s: elapsed seconds: %s', prefix, elapsed_seconds)

use example:

with _log_time_usage("sleep 1: "):
    time.sleep(1)

回答5:

There is one more option which i loves a lot now for simplicity - ipython. In ipython you got a lot of useful stuff plus:

%time <expression> - to get straight cpu and wall time on expression

%timeit <expression> - to get cpu and wall time in a loop of expression

来源：https://stackoverflow.com/questions/15707056/get-time-of-execution-of-a-block-of-code-in-python-2-7

标签

python

python-2.7

profiler