并发编程之线程

1 什么是线程:
    进程其实一个资源单位,而进程内的线程才是cpu上的执行单位
    线程其实指的就是代码的执行过程

2 为何要用线程:
    线程vs进程
        1. 同一进程下的多个线程共享该进程内的资源
        2. 创建线程的开销要远远小于进程

3 如何用线程:
方式一:

from threading import Thread
import time

def task(name):
    print('%s is running' %name)
    time.sleep(2)
    print('%s is done' %name)

if __name__ == '__main__':
    t=Thread(target=task,args=('线程1',))
    t.start()
    print('主')


方式二:
from threading import Thread
import time

class Mythread(Thread):
    def run(self):
        print('%s is running' %self.name)
        time.sleep(2)
        print('%s is done' %self.name)

if __name__ == '__main__':
    t=Mythread()
    t.start()
    print('主')

线程特性:

from threading import Thread
import time

n=100
def task():
    global n
    n=0

if __name__ == '__main__':
    t=Thread(target=task)
    t.start()
    t.join()
    print('主',n)


from threading import Thread
import time,os

def task():
    print('%s is running' %os.getpid())

if __name__ == '__main__':
    t=Thread(target=task)
    t.start()
    print('主',os.getpid())


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

def task():
    print('%s is running' %current_thread().name)
    time.sleep(2)

if __name__ == '__main__':
    t=Thread(target=task,)
    t.start()
    # t.join()
    # print('主',active_count())
    print('主',current_thread().name)

守护线程:

from threading import Thread
import time

def task(name):
    print('%s is running' %name)
    time.sleep(2)
    print('%s is done' %name)

if __name__ == '__main__':
    t=Thread(target=task,args=('线程1',))
    t.daemon=True
    t.start()
    print('主')


from threading import Thread
from multiprocessing import Process
import time
def foo():
    print(123)
    time.sleep(1)
    print("end123")

def bar():
    print(456)
    time.sleep(3)
    print("end456")

if __name__ == '__main__':
    # t1=Thread(target=foo)
    # t2=Thread(target=bar)

    t1=Process(target=foo)
    t2=Process(target=bar)
    t1.daemon=True
    t1.start()
    t2.start()
    print("main-------")

    '''
    123
    main-------
    456
    end456
    '''

    '''
    main-------
    123
    456
    end456
    '''

    '''
    main-------
    456
    end456
    '''

互斥锁:

from threading import Thread,Lock
import time

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

if __name__ == '__main__':
    t_l=[]
    for i in range(100):
        t=Thread(target=task)
        t_l.append(t)
        t.start()

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