#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
time.sleep(0.1) # 时间长，线程切换变量就覆盖
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 99
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
time.sleep(0.0001) # 时间长，线程切换变量就覆盖
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 65
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
time.sleep(0.00001) # 时间长，线程切换变量就覆盖
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 54
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
print('ok')
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
ok
ok
ok
ok
ok
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ok
ok
ok
ok
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ok
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okok
ok
ok
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okok
ok
okok
okok
ok
ok
ok
ok
final num: 41
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
import time
import threading
def addNum():
global num #在每个线程中都获取这个全局变量
print('ok')
num -= 1 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
# temp = num
# print('ok')
# num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
ok
ok
ok
ok
okok
ok
ok
ok
ok
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okok
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ok
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okok
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ok
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ok
ok
ok
okok
ok
ok
ok
okok
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
print('ok')
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
ok
ok
ok
ok
okok
ok
ok
ok
ok
ok
ok
ok
ok
ok
ok
okok
ok
ok
ok
okok
ok
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ok
ok
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okok
ok
ok
okok
ok
okok
okok
ok
okok
ok
ok
okok
ok
final num: 50
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
# print('ok')
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
temp = num
time.sleep(0.1)
num = temp - 1
num = 100 #设定一个共享变量
thread_list = []
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 99
Process finished with exit code 0
注意：
1：why num-=1没有问题呢？这是因为动作太快（完成这个动作在切换的世界内）
2：if sleep(1)，现象会更明显，100个线程每一个一定都没有执行完就进行了切换，我们说过sleep就等效于IO阻塞，1s之内不会切换回来，所以最后的结果一定是99
多个线程都在同时操作同一个共享资源，所以会造成了资源破坏，怎么办呢？
有同学会想用join呗，但join会把整个线程给停住，造成了串行，失去了多线程的意义，而我们只需要把计算（涉及到操作公共数据）的时候串行执行。
我们可以通过同步锁来解决这种问题
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
r.acquire() #加锁,使用锁只是加锁和解锁之间的代码执行使用串行，但是前面和后面还是多线性。
temp = num
time.sleep(0.00001)
num = temp - 1
r.release() # 解锁，仅计算的程序变成串行，锁的是线程。
num = 100 #设定一个共享变量
thread_list = []
r = threading.Lock() #声明一把锁对象
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
r.acquire() #加锁,使用锁只是加锁和解锁之间的代码执行使用串行，但是前面和后面还是多线性。
temp = num
time.sleep(1)
num = temp - 1
r.release() # 解锁，仅计算的程序变成串行，锁的是线程。
num = 100 #设定一个共享变量
thread_list = []
r = threading.Lock() #声明一把锁对象
for i in range(10):
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 90
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
# r.acquire() #加锁,使用锁只是加锁和解锁之间的代码执行使用串行，但是前面和后面还是多线性。
temp = num
time.sleep(0.01)
num = temp - 1
# r.release() # 解锁，仅计算的程序变成串行，锁的是线程。
num = 100 #设定一个共享变量
thread_list = []
r = threading.Lock() #声明一把锁对象
for i in range(100):
t = threading.Thread(target=addNum)
t.start()
t.join() #使用join()整个程序会变成串行
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
final num: 0
Process finished with exit code 0
#!/usr/bin/env python3.8
# -*- coding: UTF-8 -*-
# __author: smoke
# file: syn_lock
# time: 2021/04/01
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 #num -= 1的时候cpu不能切换，好在num-=1不够cpu切换时间，当再把num赋值给别的变量就会出问题
print('ok')
r.acquire() #加锁,使用锁只是加锁和解锁之间的代码执行使用串行，但是前面和后面还是多线性。
temp = num
time.sleep(0.01)
num = temp - 1
r.release() # 解锁，仅计算的程序变成串行，锁的是线程。
num = 100 #设定一个共享变量
thread_list = []
r = threading.Lock() #声明一把锁对象
for i in range(100):
t = threading.Thread(target=addNum)
t.start()
# t.join() #使用join()整个程序会变成串行
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)
/home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/venv/bin/python /home/smoke/文档/DocumentFile/PycharmProjects/pythonProject/join/syn_lock.py
ok
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final num: 0
Process finished with exit code 0
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