Python线程，进程

线程，进程：线程是操作系统能够进行运算调度的最小单位。
一个线程就是一堆指令集合

GIL：（Global Interpreter Lock 全局解释器锁）只有cpython有GIL。 作用：在同一时刻只能有一个线程进入解释器，因为有GIL的存在，所以Python不能使用多个处理器同时处理多个线程。
GIL是加在解释器上的。

进程：一个程序的实例，可以多进程处理
线程可以数据共享，进程不能实现共享
结论：在Python里如果处理的任务是IO密集型的，可以用多线程，如果是计算密集型的，改C。

join是阻塞用的，在子线程完成运行之前，这个子线程的父线程将一直被阻塞。
daemon守护线程（主线程结束之后不再等待子线程运行，直接结束）

#线程就是一堆指令集import timeimport threadingbegin=time.time()def foo(n):    print('foo%s'%n)    time.sleep(1)  #不占CPU    print('end foo')def bar(n):    print('bar%s'%n)    time.sleep(2)    print('end bar')# foo()# bar()t1=threading.Thread(target=foo,args=(1,))t2=threading.Thread(target=bar,args=(2,))t1.start()t2.start()print('.....in the main........')t1.join()t2.join()end=time.time()print(end-begin)====================================================================================

from time import ctime,sleepimport threadingdef music(func):    for i in range(2):        print('i was listening to %s,%s'%(func,ctime()))        sleep(1)        print('end listening %s'%ctime())def move(func):    for i in range(2):        print('i was watching at the %s! %s'%(func,ctime()))        sleep(5)        print('end watching at the %s'%ctime())threads=[]t1=threading.Thread(target=music,args=('七里香,',))threads.append(t1)t2=threading.Thread(target=move,args=('阿甘正传,',))threads.append(t2)if __name__=='__main__':    # music(u'七里香')    # move(u'世界末路')    t2.setDaemon(True)    for t in threads:        # t.setDaemon(True)        t.start()        # t.join()    # t.join()    print('all over is %s'%ctime())print(threading.current_thread()) #当前执行的线程print(threading.active_count()) #当前或者的线程print()# =========================通过类创建线程===============================import threadingimport timeclass MyThread(threading.Thread):    def __init__(self, num):        threading.Thread.__init__(self)        self.num = num    def run(self):  # 定义每个线程要运行的函数        print("running on number:%s" % self.num)        time.sleep(3)if __name__ == '__main__':    t1 = MyThread(1)    t2 = MyThread(2)    t1.start()    t2.start()===================================================================================同步锁

import timeimport threadingdef addNum():    global num #在每个线程中都获取这个全局变量    # num-=1  #最后结果是0,执行很快，CPU来不及切换，所以不会产生死锁    #开锁 acquire ，解锁 release    r.acquire()    temp=num    print('ok')    time.sleep(0.01)    num =temp-1 #对此公共变量进行-1操作    r.release()num = 100  #设定一个共享变量thread_list = []#加锁r=threading.Lock()for i in range(100):    t = threading.Thread(target=addNum)    t.start()    # t.join() #程序变成串行    thread_list.append(t)for t in thread_list: #等待所有线程执行完毕    t.join()print('final num:', num )# import time# import threading# def addNum():#     global num #在每个线程中都获取这个全局变量#     # num-=1#     lock.acquire()#     temp=num#     print('--get num:',num )#     time.sleep(0.01)#     num =temp-1 #对此公共变量进行-1操作#     lock.release()# num = 100  #设定一个共享变量# thread_list = []# lock=threading.Lock()# for i in range(100):#     t = threading.Thread(target=addNum)#     t.start()#     thread_list.append(t)## # for t in thread_list: #等待所有线程执行完毕# #     t.join()## print('final num:', num )==================================================================================死锁和递归锁

import threading,timeclass myThread(threading.Thread):    def doA(self):        # lockA.acquire()        lock.acquire()        print(self.name,"gotlockA1",time.ctime())        time.sleep(3)        # lockB.acquire()        lock.acquire()        print(self.name,"gotlockB1",time.ctime())        # lockB.release()        # lockA.release()        lock.release()        lock.release()    def doB(self):        # lockB.acquire()        lock.acquire()        print(self.name,"gotlockB2",time.ctime())        time.sleep(2)        # lockA.acquire()        lock.acquire()        print(self.name,"gotlockA2",time.ctime())        # lockA.release()        # lockB.release()        lock.release()        lock.release()    def run(self):        self.doA()        time.sleep(0.1)        self.doB()if __name__=="__main__":    # lockA=threading.Lock()    # lockB=threading.Lock()    lock=threading.RLock() #递归锁，将上面的lockA和lockB全部替换成lock    threads=[]    for i in range(5):        threads.append(myThread())    for t in threads:        t.start()    for t in threads:        t.join()#等待线程结束，后面再讲。#===============================================================class Account():    def __int__(self,id,money,r):        self.id=id        self.balance=money    def withdraw(self,num):        r.acquire()        self.balance-=num        r.release()    def repay(self,num):        r.acquire()        self.balance+=num        r.release()    def abc(self,num):        r.acquire()        self.withdraw()        self.balance+=num        r.release()def transer(_from,to,count):    r.acquire()    _from.withdraw(count)    to.repay(count)    r.release()r=threading.RLock()a1=Account('alex',10)a2=Account('abc',20)t1=threading.Thread(target=transer,args=(a1,a2,100))t2=threading.Thread(target=transer,args=(a2,a1,200))t1.start()t2.start()

来源：https://www.cnblogs.com/cxli99/p/8869018.html