from multiprocessing import Process
import os
import time

nums = [11, 22]


def work1():
  """子进程要执行的代码"""
  print("in process1 pid=%d ,nums=%s" % (os.getpid(), nums))
  for i in range(3):
    nums.append(i)
    time.sleep(1)
    print("in process1 pid=%d ,nums=%s" % (os.getpid(), nums))


def work2():
  """子进程要执行的代码"""
  print("in process2 pid=%d ,nums=%s" % (os.getpid(), nums))


if __name__ == '__main__':
  p1 = Process(target=work1)
  p1.start()
  p1.join()

  p2 = Process(target=work2)
  p2.start()

from multiprocessing import Queue
# 初始化一个Queue对象，最多可接收三条put消息
q = Queue(3) 
q.put("消息1")
q.put("消息2")
print(q.full()) # False
q.put("消息3")
print(q.full()) # True

# 因为消息队列已满下面的try都会抛出异常
# 第一个try会等待2秒后再抛出异常
try:
  q.put("消息4", True, 2)
except:
  print("消息队列已满，现有消息数量:%s" % q.qsize())
# 第二个Try会立刻抛出异常
try:
  q.put_nowait("消息4")
except:
  print("消息列队已满，现有消息数量:%s" % q.qsize())

# 推荐的方式，先判断消息列队是否已满，再写入
if not q.full():
  q.put_nowait("消息4")

# 读取消息时，先判断消息列队是否为空，再读取
if not q.empty():
  for i in range(q.qsize()):
    print(q.get_nowait())

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


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


def read(q):
  # 读数据进程执行的代码:
  while True:
    if not q.empty():
      value = q.get(True)
      print('Get %s from queue.' % value)
      time.sleep(random.random())
    else:
      break


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()
  # 等待pw结束:
  pw.join()
  # 启动子进程pr，读取:
  pr.start()
  pr.join()
  print('')
  print('所有数据都写入并且读完')