python语句性能分析

1、for语句性能优于while

import time

if __name__ == '__main__':
    start_time = time.time()
    for i in range(10 ** 8):
        pass
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)
    i = 0
    start_time = time.time()
    while i < 10 ** 8:
        i += 1
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)

运行结果：

2、max函数性能劣于直接判断：

import time

if __name__ == '__main__':
    maxl = 0
    start_time = time.time()
    for i in range(10 ** 8):
        maxl = max(maxl, i)
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)

    maxl = 0
    start_time = time.time()
    for i in range(10 ** 8):
        if i > maxl: maxl = i
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)

运行结果：

3、数组的读取速度优于字典：

import time

if __name__ == '__main__':
    n = 1000

    start_time = time.time()
    m1 = [[0] * n for _ in range(n)]
    for i in range(n):
        for j in range(n):
            m1[i][j] = 1
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)

    start_time = time.time()
    m2 = {}
    for i in range(n):
        for j in range(n):
            m2[i, j] = 1
    end_time = time.time()
    run_time = end_time - start_time
    print(run_time)

运行结果：

注：环境选用python3.9