并发编程

一、线程的使用

import threading
def func(arg):
    print(arg)

t = threading.Thread(target=func,args=(11,))
t.start()

print(123)

import threading
import time
def func(arg):
    time.sleep(arg)
    print(arg)

t1 = threading.Thread(target=func,args=(3,))
t1.start()

t2 = threading.Thread(target=func,args=(9,))
t2.start()

print(123)

import threading
import time
def func(arg):
    time.sleep(2)
    print(arg)

t1 = threading.Thread(target=func,args=(3,))
t1.setDaemon(True)
t1.start()

t2 = threading.Thread(target=func,args=(9,))
t2.setDaemon(True)
t2.start()

print(123)

import threading
import time
def func(arg):
    time.sleep(0.01)
    print(arg)

print('创建子线程t1')
t1 = threading.Thread(target=func,args=(3,))
t1.start()
# 无参数，让主线程在这里等着，等到子线程t1执行完毕，才可以继续往下走。
# 有参数，让主线程在这里最多等待n秒，无论是否执行完毕，会继续往下走。
t1.join(2)

print('创建子线程t2')
t2 = threading.Thread(target=func,args=(9,))
t2.start()
t2.join(2) # 让主线程在这里等着，等到子线程t2执行完毕，才可以继续往下走。

print(123)

import threading
def func(arg):
    # 获取当前执行该函数的线程的对象
    t = threading.current_thread()
    # 根据当前线程对象获取当前线程名称
    name = t.getName()
    print(name,arg)

t1 = threading.Thread(target=func,args=(11,))
t1.setName('侯明魏')
t1.start()

t2 = threading.Thread(target=func,args=(22,))
t2.setName('刘宁钱')
t2.start()

print(123)

import threading
# 先打印：11？123？
def func(arg):
    print(arg)

t1 = threading.Thread(target=func,args=(11,))
t1.start()
# start 是开始运行线程吗？不是
# start 告诉cpu，我已经准备就绪，你可以调度我了。
print(123)

import threading
# 多线程方式：1 (常见)
def func(arg):
    print(arg)

t1 = threading.Thread(target=func,args=(11,))
t1.start()

# 多线程方式：2
class MyThread(threading.Thread):

    def run(self):
        print(11111,self._args,self._kwargs)

t1 = MyThread(args=(11,))
t1.start()

t2 = MyThread(args=(22,))
t2.start()

print('end')

 二、多线程

import threading
v1 = [11,22,33] # +1
v2 = [44,55,66] # 100

def func(data,plus):
    for i in range(len(data)):
        data[i] = data[i] + plus

t1 = threading.Thread(target=func,args=(v1,1))
t1.start()

t2 = threading.Thread(target=func,args=(v2,100))
t2.start()

import threading
import requests
import uuid

url_list = [
    'https://www3.autoimg.cn/newsdfs/g28/M05/F9/98/120x90_0_autohomecar__ChsEnluQmUmARAhAAAFES6mpmTM281.jpg',
    'https://www2.autoimg.cn/newsdfs/g28/M09/FC/06/120x90_0_autohomecar__ChcCR1uQlD6AT4P3AAGRMJX7834274.jpg',
    'https://www2.autoimg.cn/newsdfs/g3/M00/C6/A9/120x90_0_autohomecar__ChsEkVuPsdqAQz3zAAEYvWuAspI061.jpg',
]

def task(url):
    ret = requests.get(url)
    file_name = str(uuid.uuid4()) + '.jpg'
    with open(file_name, mode='wb') as f:
        f.write(ret.content)

for url in url_list:

    t = threading.Thread(target=task,args=(url,))
    t.start()

import time
import threading

lock = threading.RLock()

n = 10

def task(i):
    print('这段代码不加锁',i)

    lock.acquire() # 加锁，此区域的代码同一时刻只能有一个线程执行
    global n
    print('当前线程',i,'读取到的n值为：',n)
    n = i
    time.sleep(1)
    print('当前线程',i,'修改n值为：',n)
    lock.release() # 释放锁


for i in range(10):
    t = threading.Thread(target=task,args=(i,))
    t.start()