python lib timeit 测试运行时间

1. 简介
- 1.1. python interface
2. 案例
- 2.1. timeit() /repeat()
- 2.2. timer()

1. 简介

27.5. timeit — Measure execution time of small code snippets

Source code: Lib/timeit.py

timeit模块可以用来测试一段代码的执行耗时，如一个变量赋值语句的执行时间，一个函数的运行时间。

timeit是标准模块，无需安装。

import timeit

1.1. python interface

模块定义了三个方法和一个公共类。

1.1.1. timeit.timeit(stmt='pass', setup='pass', timer=, number=1000000, globals=None)

Create a Timer instance with the given statement, setup code and timer function and run its timeit() method with number executions. The optional globals argument specifies a namespace in which to execute the code.

参数说明：

stmt:测试代码，一般用函数（可以用字符串表达式）。
setup:传入stmt的运行环境，如参数，变量，模块。
timer:
number:执行次数，默认1000000
globals:

1.1.2. timeit.repeat(stmt='pass', setup='pass', timer=, repeat=3, number=1000000, globals=None)

Create a Timer instance with the given statement, setup code and timer function and run its repeat() method with the given repeat count and number executions. The optional globals argument specifies a namespace in which to execute the code.

参数说明:

repeat:重复次数，每次的结果构成列表返回，默认3次。

1.1.3. timeit.default_timer()

The default timer, which is always time.perf_counter().

Changed in version 3.3: time.perf_counter() is now the default timer.

1.1.4. class timeit.Timer(stmt='pass', setup='pass', timer=, globals=None)

Class for timing execution speed of small code snippets.

2. 案例

2.1. timeit() /repeat()

注意事项：

方法应在setup参数中导入；
变量需在setup参数中导入，且变量应为全局变量或直接传入；
测试次数number默认为10**6，注意修改，特别是单次执行时间较长时。

import timeit

def _test_timeit():

    global a

    # timeit

    a = [1,2,3,4]

    t = timeit.timeit(stmt='_test_2(a)',

                      setup='from __main__ import _test_2, a',

                      number=100000)

    print(t)

    # repeat

    a = [1,2,3,4]

    t = timeit.repeat(stmt='_test_2(a)',

                      setup='from __main__ import _test_2, a',

                      number=1000000,

                      repeat=5 )

    print(t)

def _test_2(s=None, *ar):

    #s.insert(0, 45)

    s.append(55)

if __name__ == '__main__':

    a = None

    _test_timeit()

    pass

输出：

0.02622983706364665

[0.28630844773090425, 0.2964419925588122, 0.23573263042489412, 0.2578145301438086, 0.22425034115163478]

说明：

repeat()与timeit()的区别在于它会重复测试多次，返回单次执行时间所组成的列表。

2.2. timer()

timer()实质是timeit()和repeat()的底层实现；

def timeit(stmt="pass", setup="pass", timer=default_timer,

           number=default_number, globals=None):

    """Convenience function to create Timer object and call timeit method."""

    return Timer(stmt, setup, timer, globals).timeit(number)

def repeat(stmt="pass", setup="pass", timer=default_timer,

           repeat=default_repeat, number=default_number, globals=None):

    """Convenience function to create Timer object and call repeat method."""

    return Timer(stmt, setup, timer, globals).repeat(repeat, number)

也可以使用Timer()初始化然后调用其方法timeit和repeat。