Python开发之进程与线程概述

import os

print('Process (%s) start...' % os.getpid())
# Only works on Unix/Linux/Mac:
pid = os.fork()
if pid == 0:
    print('I am child process (%s) and my parent is %s.' % (os.getpid(), os.getppid()))
else:
    print('I (%s) just created a child process (%s).' % (os.getpid(), pid))
    
# Process (44587) start...
# I (44587) just created a child process (44588).
# I am child process (44588) and my parent is 44587.

import os
import time

# 子进程要执行的代码
def run_proc(name):
    time.sleep(1)
    print('Run child process %s (%s)...' % (name, os.getpid()))

if __name__=='__main__':
    print('Parent process %s.' % os.getpid())
    p = Process(target=run_proc, args=('test',))    # args里面为何要用,隔开？
    p.start()                                        # 子进程启动，不加这个子进程不执行
    p.join()             # 等待子进程p的执行完毕后再向下执行，不加此项，主程序执行完毕，子进程依然会继续执行不受影响
    print('Child process end.'),

# Parent process 8428.
# Run child process test (9392)...
# Child process end.

from multiprocessing import Pool,cpu_count
import os, time, random

def long_time_task(name):
    print('Run task %s (%s)...' % (name, os.getpid()))
    start = time.time()
    time.sleep(random.random() * 3)
    end = time.time()
    print('Task %s runs %0.2f seconds.' % (name, (end - start)))

def Bar(arg):
    print('-->exec done:',arg,os.getpid())

if __name__=='__main__':
    print('Parent process %s.' % os.getpid())
    p = Pool(cpu_count())               # 获取当前cpu核数，多核cpu的情况下多进程才能实现真正的并发
    for i in range(5):
        # p.apply_async(func=long_time_task, args=(i,), callback=Bar) #callback回调 执行完func后再执行callback 用主程序执行
        p.apply_async(long_time_task, args=(i,))
    print('Waiting for all subprocesses done...')
    p.close()
    p.join()              # ！等待进程池执行完毕，不然主进程执行完毕后，进程池直接关闭
    print('All subprocesses done.')

# Parent process 4492.
# Waiting for all subprocesses done...
# Run task 0 (3108)...
# Run task 1 (7936)...
# Run task 2 (11236)...
# Run task 3 (8284)...
# Task 2 runs 0.86 seconds.
# Run task 4 (11236)...
# Task 0 runs 1.34 seconds.
# Task 1 runs 1.49 seconds.
# Task 3 runs 2.62 seconds.
# Task 4 runs 1.90 seconds.
# All subprocesses done.

p = Pool(5)

from multiprocessing import Process, Queue
import os, time, random

# 写数据进程执行的代码:
def write(q):
    print('Process to write: %s' % os.getpid())
    for value in ['A', 'B', 'C']:
        print('Put %s to queue...' % value)
        q.put(value)
        time.sleep(random.random())

# 读数据进程执行的代码:
def read(q):
    print('Process to read: %s' % os.getpid())
    while True:
        value = q.get(True)
        print('Get %s from queue.' % value)

if __name__=='__main__':
    # 父进程创建Queue，并传给各个子进程：
    q = Queue()
    pw = Process(target=write, args=(q,))
    pr = Process(target=read, args=(q,))
    # 启动子进程pw，写入:
    pw.start()
    # 启动子进程pr，读取:
    pr.start()
    # 等待pw结束:
    pw.join()
    # pr进程里是死循环，无法等待其结束，只能强行终止:
    pr.terminate()      # 强制关闭子进程

# Process to write: 9472
# Put A to queue...
# Process to read: 3948
# Get A from queue.
# Put B to queue...
# Get B from queue.
# Put C to queue...
# Get C from queue.

from multiprocessing import Process, Manager
import os

# manager = Manager()
vip_list = []
#vip_list = manager.list()

def testFunc(cc):
    vip_list.append(cc)
    print 'process id:', os.getpid()

if __name__ == '__main__':
    threads = []

    for ll in range(10):
        t = Process(target=testFunc, args=(ll,))
        t.daemon = True
        threads.append(t)

    for i in range(len(threads)):
        threads[i].start()

    for j in range(len(threads)):
        threads[j].join()

    print "------------------------"
    print 'process id:', os.getpid()
    print vip_list

# process id: 9436
# process id: 11120
# process id: 10636
# process id: 1380
# process id: 10976
# process id: 10708
# process id: 2524
# process id: 9392
# process id: 10060
# process id: 8516
# ------------------------
# process id: 9836
# []

from multiprocessing import Process, Value, Array

def f(n, a):
    n.value = 3.1415927
    for i in range(len(a)):
        a[i] = -a[i]

if __name__ == '__main__':
    num = Value('d', 0.0)
    arr = Array('i', range(10))

    p = Process(target=f, args=(num, arr))
    p.start()
    p.join()

    print num.value
    print arr[:]
    
# 3.1415927
# [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]

from multiprocessing import Process, Manager

def f(d, l):
    d[1] = '1'
    d['2'] = 2
    d[0.25] = None
    l.reverse()

if __name__ == '__main__':
    manager = Manager()

    d = manager.dict()
    l = manager.list(range(10))

    p = Process(target=f, args=(d, l))
    p.start()
    p.join()

    print d
    print l

# {0.25: None, 1: '1', '2': 2}
# [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]