029 timeit

测量生成列表的时间

• 像是 C, Js 中把函数作为参数传入

>>> import timeit
>>> func = '''
... arr = []
... for i in range(1000):
...   arr.append(i)
... '''
>>> t1 = timeit.timeit(stmt=func, number=10000)  # 可近似看成函数指针
>>> t2 = timeit.timeit(stmt="[i for i in range(1000)]", number=10000)
>>> t1
1.0912232999999105
>>> t2
0.5270981999999549

• 可以看出，列表生成式比 list.append() 快

测量函数运行时间

例1

import timeit


def func(num=3):
    for i in range(num):
        print(f"Repeat for {i}.")


if __name__ == "__main__":
    t = timeit.timeit(stmt=func, number=5)
    print(t)

>>>

Repeat for 0.
Repeat for 1.
Repeat for 2.
Repeat for 0.
Repeat for 1.
Repeat for 2.
Repeat for 0.
Repeat for 1.
Repeat for 2.
Repeat for 0.
Repeat for 1.
Repeat for 2.
Repeat for 0.
Repeat for 1.
Repeat for 2.
0.0009049000000231899

例2

import timeit


def func(num=3):
    for i in range(num):
        print(f"Repeat for {i}.")


if __name__ == "__main__":
    t = timeit.timeit(stmt=func, setup="func"+"num=5", number=5)
    # t = timeit.timeit(func, setup="funcnum=5", number=5) 也行，但不直观
    print(t)

>>>

Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
0.008177499999874271

例3

>>> s = '''
... def func(num):
...   for i in range(num):
...     print(f"Repeat for {i}")
... '''
>>> t = timeit.timeit(stmt="func(num)", setup=s+"num=3", number=5)
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
Repeat for 0
Repeat for 1
Repeat for 2
>>> t
0.0020025999997415056