如果現在需要在多處加鎖大於等於2的時候 因為計算機比較笨，當他鎖上一把鎖的時候又所理一把鎖，等他來開鎖的時候他不知道用哪把鑰匙來開鎖，

所以這個時候我們需要把把平常的鎖變為迭代鎖

eg：

import threading
import time

local = threading.RLock()
# 迭代加鎖首先生成例項
def run(name):
    global num
    local.acquire()  # 上鎖
    num += 1
    run2(num)
    local.release()  # 解鎖
    print(threading.active_count())

 
def run2(num):
    local.acquire()
    num += 1
    run3(num)
    local.release()

def run3(num):
    local.acquire()
    num+=1
    local.release()

num = 0
py_res = []
for i in range(50):
    t = threading.Thread(target=run,args=('t%s'%i,))
    py_res.append(t)
    t.start()


for i in py_res:
    i.join()

 
print("num : %s"% num)

型號量可以控制同線程的個數，和鎖的用法一樣

import threading
import time
senm = threading.BoundedSemaphore(5)
def run(num):
    senm.acquire()  # 上鎖
    time.sleep(2)
    print('run the thread %s' % num)
    senm.release()  # 解鎖

for i in range(50):
    t = threading.Thread(target=run, args=('
 
%s' % i,))
    t.start()
    print(threading.active_count())

while threading.active_count() != 1:
    pass
else:
    print('is done')