并发编程——多线程

1.什么是线程
    进程:资源单位
    线程:执行单位
    注意:每一个进程中都会自带一个线程

2.为什么要有线程
    开一个进程:
        申请内存空间   耗时
        将代码拷贝到申请的内存空间中   耗时
    开线程:
        不需要申请内存空间

    开线程的开销远远小于开进程的开销！！！
3.如何使用线程

4 子线程的两种建立方式

# 方式1

'''
from threading import Thread
import time


def task(name):
    print('%s is running' % name)
    time.sleep(1)
    print('%s is over')


t = Thread(target=task, args=('king',))
t.start()
print('主')
'''


# 方式 2
from threading import Thread
import time

class MyThread(Thread):
    def __init__(self,name):
        super().__init__()
        self.name = name

    def run(self):
        print('%s is run'%self.name)
        time.sleep(3)
        print('%s is over'%self.name)

t = MyThread('king')
t.start()
print('主')

5、线程之间的数据共享

from threading import Thread

x = 100

def task():
    global x
    x =666
    print(x)

t = Thread(target=task)
t.start()
print(x)

6、线程互斥锁

from threading import Thread,Lock

import time

mutex = Lock()
n = 100
def task():
    global n
    mutex.acquire()
    tmp = n
    time.sleep(0.1)
    n = tmp -1
    mutex.release()

t_list = []
for i in range(100):
    t = Thread(target=task)
    t.start()
    t_list.append(t)

for t in t_list:
    t.join()
print(n)

7、线程的其他属性方法

from threading import Thread,active_count,current_thread
import os
import time


def task(name):
    # print('%s is running'%name,os.getpid())
    print('%s is running'%name,current_thread().name,current_thread().getName())
    time.sleep(1)
    print('%s is over'%name)

def info(name):
    print('%s is running' % name, current_thread().name, current_thread().getName())
    time.sleep(1)
    print('%s is over' % name)

t = Thread(target=task,args=('关磊',))
t1 = Thread(target=info,args=('关超',))
t.start()
t1.start()
t.join()
print(active_count())  # 当前存活的线程数
print(os.getpid())
print(current_thread().name)
print(current_thread().getName())