总结python多进程multiprocessing的相关知识

import multiprocessing as mp
from time import sleep

# 进程执行函数
def fun():
    print("开始一个进程")
    sleep(3)
    print("进程结束")

# 创建进程对象
p = mp.Process(target = fun)

p.start()   # 启动进程

p.join()    # 回收进程

import multiprocessing as mp
from time import sleep

# 进程执行函数
def fun():
    print("开始一个进程")
    sleep(3)
    print("进程结束")

# 创建进程对象
p = mp.Process(target = fun)    # 把fun函数作为独立子进程 其它函数由进程来执行

p.start()   # 启动进程

sleep(2)
print("父进程执行内容")

p.join()    # 回收进程
print("===============")
"""
pid = os.fork
if pid == 0
    fun()
    os._exit(0)
else:
    os.wait()
"""

import multiprocessing as mp
from time import sleep

a = 1

# 进程执行函数
def fun():
    print("开始一个进程")
    sleep(3)
    global a
    print("a=", a)
    a = 1000
    print("a=", a)
    print("进程结束")

# 创建进程对象
p = mp.Process(target = fun)    # 把fun函数作为独立子进程 其它函数由进程来执行

p.start()   # 启动进程

sleep(2)
print("父进程执行内容")

p.join()    # 回收进程
print("===============")
print("a=", a)

"""
创建多个进程
"""

from multiprocessing import Process
import os
from time import sleep

def fun1():
    sleep(2)
    print(os.getppid(), '--', os.getpid(), "吃饭")

def fun2():
    sleep(3)
    print(os.getppid(), '--', os.getpid(), "睡觉")

def fun3():
    sleep(4)
    print(os.getppid(), '--', os.getpid(), "学习")

jobs =[]

for th in [fun1, fun2, fun3]:
    p = Process(target = th)
    jobs.append(p)
    p.start()

for i in jobs:
    i.join()

from multiprocessing import Process
from time import sleep

# 含有参数的进程函数
def worker(sec, name):
    for i in range(3):
        sleep(sec)
        print("I'm %s"%name)
        print("I'm working...")

# p = Process(target = worker, args = (2, "Tom"))
p = Process(target = worker, kwargs = {'name':'tom', 'sec': 2})

p.start()
p.join()

from multiprocessing import Process
import os

filename = './dace.jpg'
size = os.path.getsize(filename)

# 复制上半部分
def up():
    fr = open(filename, 'rb')
    fw = open('bot,jpg', 'wb')
    n = size//2
    fw.write(fr.read(n))
    fw.close()
    fr.close()

# 复制下半部分
def down():
    fr = open(filename, 'rb')
    fw = open('bot,jpg', 'wb')
    fr.seek(size//2.0)
    fw.write(fr.read())
    fw.close()
    fr.close()

p = Process(target = up)
q = Process(target = down)
p.start()
q.start()
p.join()
q.join()