获取 Python 2.7 中代码块的执行时间
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Get time of execution of a block of code in Python 2.7
提问by lucacerone
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.
我想测量评估 Python 程序中的代码块所用的时间，可能将用户 cpu 时间、系统 cpu 时间和经过时间分开。
I know the timeitmodule, but I have many self-written functions and it is not very easy
to pass them in the setup process.
我知道这个timeit模块，但是我有很多自写的函数，在设置过程中传递它们不是很容易。
I would rather have something that could be used like:
我宁愿有一些可以使用的东西：
#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.
用户和系统 CPU 时间不是必需的（尽管我想测量它们），但是对于经过的时间，我希望能够做这样的事情，而不是使用复杂的命令或模块。
采纳答案by Andrew Clark
To get the elapsed time in seconds, you can use timeit.default_timer():
要以秒为单位获取经过的时间，您可以使用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.
timeit.default_timer()用于代替time.time()或time.clock()因为它将为任何平台选择具有更高分辨率的计时函数。
回答by Yarkee
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.
我总是使用装饰器为现有函数做一些额外的工作，包括获取执行时间。它是pythonic和简单的。
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by monklof
You can achieve this through the Context Manager, for example:
您可以通过上下文管理器实现这一点，例如：
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:
使用示例：
with _log_time_usage("sleep 1: "):
time.sleep(1)
回答by Michael Herrmann
I found myself solving this problem again and again, so I finally created a libraryfor it. Install with pip install timer_cm. Then:
我发现自己一次又一次地解决了这个问题，所以我终于为它创建了一个库。安装pip install timer_cm. 然后：
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:
输出：
Long task: 3.520s
Baby steps: 2.518s (71%)
First step: 1.001s (28%)
回答by valex
There is one more option which i loves a lot now for simplicity - ipython. In ipython you got a lot of useful stuff plus:
为了简单起见，我现在非常喜欢另一种选择 - ipython。在 ipython 中，你得到了很多有用的东西，另外：
%time <expression>- to get straight cpu and wall time on expression
%time <expression>- 在表达上获得直接的 CPU 和墙上时间
%timeit <expression>- to get cpu and wall time in a loop of expression
%timeit <expression>- 在表达式循环中获取 CPU 和挂机时间
回答by Christopher Peisert
Python 3 - Simple solution using standard library
Python 3 - 使用标准库的简单解决方案
Option 1: Triple quote the code
选项 1：三重引用代码
import inspect
import timeit
code_block = inspect.cleandoc("""
base = 123456789
exponent = 100
return base ** exponent
""")
print(f'\Code block: {timeit.timeit(code_block, number=1)} elapsed seconds')
inspect.cleandochandles the removal of extra tabs and whitespace so that blocks of code can be copied and pasted without getting indentation errors.
inspect.cleandoc处理多余的制表符和空格的删除，以便可以复制和粘贴代码块而不会出现缩进错误。
Option 2: Place code block in a function
选项 2：将代码块放在函数中
import timeit
def my_function():
base = 123456789
exponent = 100
return base ** exponent
if __name__ == '__main__':
print(f'With lambda wrapper: {timeit.timeit(lambda: my_function(), number=1)} elapsed seconds')
Note that a function call will add additional execution time versus timing the function body directly.
请注意，与直接为函数体计时相比，函数调用会增加额外的执行时间。
