python-实用

装饰器

闭包函数的语法糖。

浅拷贝和深拷贝

引用与复制
python中赋值语句都是引用。
拷贝就是复制。

浅拷贝

b = a[::] 切片复制

深拷贝

import copy
a = [0, [1, 2], 3]
b = copy.deepcopy(a)
print(a, b)
a[1][0] = 0
print(a, b)
b[1][0] = 2
print(a, b)

多线程

treading模块

import time
import threading
# 左手画圆
def draw_circle(cost):
    print("start draw a circle ", time.ctime())
    time.sleep(cost)
    print("draw a circle ", time.ctime())

# 右手画方
def draw_square(cost):
    print("start draw a squre", time.ctime())
    time.sleep(cost)
    print("draw a squre ", time.ctime())

def multi_thread():
    draw_circle_thread = threading.Thread(target=draw_circle, args=(1,))
    draw_square_thread = threading.Thread(target=draw_square, args=(2,))
    draw_circle_thread.start()
    draw_square_thread.start()

if __name__ == '__main__':
    print("start", time.ctime())
    multi_thread()
    print("end", time.ctime())

补充两个设置语句join：

import time
import threading
# 左手画圆
def draw_circle(cost):
    print("start draw a circle ", time.ctime())
    time.sleep(cost)
    print("draw a circle ", time.ctime())

# 右手画方
def draw_square(cost):
    print("start draw a squre", time.ctime())
    time.sleep(cost)
    print("draw a squre ", time.ctime())

def multi_thread():
    draw_circle_thread = threading.Thread(target=draw_circle, args=(1,))
    draw_square_thread = threading.Thread(target=draw_square, args=(2,))
    draw_circle_thread.start()
    draw_square_thread.start()
    draw_circle_thread.join() //调用join之后主线程会等待子线程完成之后才往下走
    draw_square_thread.join() //

if __name__ == '__main__':
    print("start", time.ctime())
    multi_thread()
    print("end", time.ctime())