进程创建的两种方式
第一种方法:
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
# 在windows环境下, 开启进程必须在__name__ == '__main__'下面
p = Process(target=task, args=("常鑫",)) # 创建一个进程对象
p.start() # 只是向操作系统发出一个开辟子进程的信号,然后就执行下一行了
# 这个信号操作系统接收到之后, 会从内存中开辟一个子进程空间, 然后再将主进程所有数据copy加载到子进程, 然后再调用CPU去执行
# 开辟子进程开销是很大的
print("==主开始")
"""
==主开始
常鑫 is running
常鑫 is gone
"""
第二种方法:
from multiprocessing import Process
import time
class MyProcess(Process):
def __init__(self, name):
super().__init__()
self.name = name
def run(self):
print(f"{self.name} is running")
time.sleep(2)
print(f"{self.name} is gone")
if __name__ == '__main__':
p = MyProcess('常鑫')
p.start()
print('===主程序')
"""
===主程序
常鑫 is running
常鑫 is gone
"""
简单应用
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(1)
print(f"{name} is gone")
def task1(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
def task2(name):
print(f"{name} is running")
time.sleep(3)
print(f"{name} is gone")
# 一个进程串行的执行三个任务
if __name__ == '__main__':
start_time = time.time()
task("常鑫")
task1("李远点业")
task2("海狗")
print(f"结束时间{time.time() - start_time}")
"""
常鑫 is running
常鑫 is gone
李远点业 is running
李远点业 is gone
海狗 is running
海狗 is gone
结束时间6.001969337463379
"""
# 三个进程 并发或者并行的执行三个任务
if __name__ == '__main__':
p1 = Process(target=task, args=("常鑫",))
p2 = Process(target=task1, args=("李远点业",))
p3 = Process(target=task2, args=("海狗",))
start_time = time.time()
p1.start()
p2.start()
p3.start()
time.sleep(5)
print(f"结束时间{time.time() - start_time}")
"""
常鑫 is running
李远点业 is running
海狗 is running
常鑫 is gone
李远点业 is gone
海狗 is gone
结束时间5.026661396026611
"""
进程pid
获取进程pid
import os
import time
print(f'子进程:{os.getpid()}')
print(f'主进程:{os.getppid()}')
time.sleep(50)
# 第一次执行
"""
子进程:139000
主进程:109036
"""
# 第二次执行
"""
子进程:136820
主进程:109036
"""
# 第三次执行
"""
子进程:139916
主进程:109036
"""
from multiprocessing import Process
import os
def task(name):
print(f"子进程{os.getpid()}")
print(f"主进程{os.getppid()}")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫",))
p.start()
print(f"===={os.getpid()}")
"""
====142800
子进程143244
主进程142800
"""
# 创建的进程的主进程就是 本模块此进程
验证进程之间的空间隔离
from multiprocessing import Process
import time
name = '太白'
def task():
global name
name = "刚子sb"
print(f"子进程:{name}")
if __name__ == '__main__':
p = Process(target=task)
p.start()
time.sleep(3)
print(f"主:{name}")
"""
子进程:刚子sb
主:太白
"""
# 子进程的name变量即使有global也没有重新赋值, 因为进程之间的空间隔离
lst = ["丽丽", ]
from multiprocessing import Process
import time
def task():
lst.append('怼姐')
print(f"子进程{lst}")
if __name__ == '__main__':
p = Process(target=task)
p.start()
time.sleep(3)
print(f"主:{lst}")
"""
子进程['丽丽', '怼姐']
主:['丽丽']
"""
# 即使是列表也有空间隔离
进程对象join方法
单个子进程使用join
join让主进程等待子进程结束之后, 在执行主进程
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫", ))
p.start()
p.join()
print("==主进程")
"""
常鑫 is running
常鑫 is gone
==主进程
"""
多个子进程使用join
验证一:
from multiprocessing import Process
import time
def task(name,sec):
print(f"{name} is running")
time.sleep(sec)
print(f"{name} is gone")
if __name__ == '__main__':
start_time = time.time()
p1 = Process(target=task, args=("常鑫", 1))
p2 = Process(target=task, args=("李业", 2))
p3 = Process(target=task, args=("海狗", 3))
p1.start()
p2.start()
p3.start()
p1.join()
p2.join()
p3.join()
print(f"==主进程{time.time() - start_time}")
"""
常鑫 is running
李业 is running
海狗 is running
常鑫 is gone
李业 is gone
海狗 is gone
==主进程:4.285647392272949
"""
验证2:
from multiprocessing import Process
import time
def task(name,sec):
print(f"{name} is running")
time.sleep(sec)
print(f"{name} is gone")
if __name__ == '__main__':
start_time = time.time()
p1 = Process(target=task, args=("常鑫", 1))
p2 = Process(target=task, args=("李业", 2))
p3 = Process(target=task, args=("海狗", 3))
p1.start()
p2.start()
p3.start()
p1.join()
print(f"==主进程1:{time.time() - start_time}")
p2.join()
print(f"==主进程2:{time.time() - start_time}")
p3.join()
print(f"==主进程3:{time.time() - start_time}")
"""
常鑫 is running
李业 is running
海狗 is running
常鑫 is gone
==主进程1:2.2231969833374023
李业 is gone
==主进程2:3.232954502105713
海狗 is gone
==主进程3:4.242786645889282
"""
# start同时开启三个进程, 同时运行
# join就是阻塞
优化验证2:
from multiprocessing import Process
import time
def task(sec):
print(f"子进程 is running")
time.sleep(sec)
print(f"子进程 is gone")
if __name__ == '__main__':
start_time = time.time()
l1 = []
for i in range(1, 4):
p = Process(target=task, args=(i,))
l1.append(p)
p.start()
for i in l1:
i.join()
print(f"==主进程{time.time() - start_time})")
"""
子进程 is running
子进程 is running
子进程 is running
子进程 is gone
子进程 is gone
子进程 is gone
==主进程4.1986918449401855)
"""
# join就是阻塞, 主进程有join, 主进程下面的代码一律不执行, 直到进程执行完毕之后再执行
进程的其他参数
terminate(杀死)
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫", ), name="alex")
p.start()
p.terminate()
print("==主进程")
"""
==主进程
"""
# 子进程刚发出信号就杀死
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫", ), name="alex")
p.start()
time.sleep(1)
p.terminate()
print("==主进程")
"""
常鑫 is running
==主进程
"""
# 睡了一秒所以子进程start了
is_alive(判断子进程是否存活)
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫", ), name="alex")
p.start()
# p.terminate()
# p.join()
print(p.is_alive())
print("==主进程")
"""
True
==主进程
常鑫 is running
常鑫 is gone
"""
# terminate 和 join 都会使进程结束, 所以有terminate 和 join 就会返回 False
守护进程
子进程守护着主进程, 只要主进程结束, 子进程跟着就结束
from multiprocessing import Process
import time
def task(name):
print(f"{name} is running")
time.sleep(2)
print(f"{name} is gone")
if __name__ == '__main__':
p = Process(target=task, args=("常鑫", ))
p.daemon = True
p.start()
print("==主")
"""
常鑫 is running
常鑫 is gone
==主
"""