038信号量

步骤：1、新建信号量对象，设置信号量数量
2、线程执行方法中，如果能够获取信号量，则执行，信号量为0不可以获取

import  threading,time

class  MyThread(threading.Thread):
    def  run(self):
        if  sema.acquire():
            print(self.name)
            time.sleep(0.3)
            sema.release()

if __name__ == '__main__':
    sema = threading.BoundedSemaphore(5)  # sema=threading.Semaphore(5)
    thrs = []
    for i in range(100):
        thrs.append(MyThread())
    for t in thrs:
        t.start()

例子：

### 强行改的信号量

import threading
import time
class Tickets:
    def __init__(self):
    self.ticket = 100

    def sell_ticket(self):
        while self.ticket > 0:
            if loc.acquire():
                print('卖出',self.ticket,'票',threading.current_thread())
                self.ticket -= 1
                loc.release()
            time.sleep(0.0001)

if __name__ == '__main__':
    ticket = Tickets()
    t1 = threading.Thread(target=ticket.sell_ticket)
    t2 = threading.Thread(target=ticket.sell_ticket)
    t3 = threading.Thread(target=ticket.sell_ticket)
    loc = threading.Semaphore(1)
    t1.start()
    t2.start()
    t3.start()

##########38里面多生产多消费信号量实现

import time
import threading

class Res:
    def __init__(self):
        self.flag = False
        self.count = 0
        self.product = ''

    def set(self,name):
        lock_con.acquire()
        while self.flag:
            lock_con.wait()
        time.sleep(0.00001)
        self.count += 1
        self.product = ''.join([name,'**',str(self.count)])
        self.message = ''.join([self.product,'__生产者__',str(threading.current_thread())])
        print(self.message)
        self.flag = True
        lock_con.notifyAll()
        lock_con.release()

    def get_product(self):
        lock_con.acquire()
        time.sleep(0.00001)
        while not self.flag:
            lock_con.wait()
        self.message = ''.join([self.product,'__消费者__',str(threading.current_thread())])
        print(self.message)
        self.flag = False
        lock_con.notifyAll()
        lock_con.release()

class Producer(threading.Thread):
    def __init__(self,r):
        threading.Thread.__init__(self)
        self.r = r

    def run(self):
        for i in range(100):
            self.r.set('大白兔奶糖')

class Consumer(threading.Thread):
    def __init__(self,r):
        threading.Thread.__init__(self)
        self.r = r

    def run(self):
        for i in range(100):
            self.r.get_product()

if __name__ == '__main__':
    lock_con = threading.Condition()
    r = Res()
    l = []
    for i in range(5):
        l.append(Consumer(r))
    for i in range(5):
        l.append(Producer(r))
    for a in l:
        a.start()