一文了解Python并发编程的工程实现方法

from multiprocessing import Pool
def f(x):
 return x * x
if __name__ == '__main__':
 with Pool(5) as p:
  # map方法的作用是将f()方法并发地映射到列表中的每个元素
  print(p.map(f, [1, 2, 3]))
# 执行结果
# [1, 4, 9]

from multiprocessing import Process
import os
def echo(text):
 # 父进程ID
 print("Process Parent ID : ", os.getppid())
 # 进程ID
 print("Process PID : ", os.getpid())
 print('echo : ', text)
if __name__ == '__main__':
 p = Process(target=echo, args=('hello process',))
 p.start()
 p.join()
# 执行结果
# Process Parent ID : 27382
# Process PID : 27383
# echo : hello process

from multiprocessing import Pool
def f(x):
 return x * x
if __name__ == '__main__':
 with Pool(5) as p:
  # map方法的作用是将f()方法并发地映射到列表中的每个元素
  a = p.map(f, [1, 2, 3])
  print(a)
  # 异步执行map
  b = p.map_async(f, [3, 5, 7, 11])
  # b 是一个result对象，代表方法的执行结果
  print(b)
  # 为了拿到结果，使用join方法等待池中工作进程退出
  p.close()
  # 调用join方法前，需先执行close或terminate方法
  p.join()
  # 获取执行结果
  print(b.get())
# 执行结果
# [1, 4, 9]
# <multiprocessing.pool.MapResult object at 0x10631b710>
# [9, 25, 49, 121]

from multiprocessing import Process, Queue
def f(q):
 q.put([42, None, 'hello'])
if __name__ == '__main__':
 # 使用Queue进行数据通信
 q = Queue()
 p = Process(target=f, args=(q,))
 p.start()
 # 主进程取得子进程中的数据
 print(q.get()) # prints "[42, None, 'hello']"
 p.join()
# 执行结果
# [42, None, 'hello']

from multiprocessing import Process, Pipe
def write(conn):
 # 子进程中发送一个对象
 conn.send([42, None, 'hello'])
 conn.close()
def read(conn):
 # 在读的进程中通过recv接收对象
 data = conn.recv()
 print(data)
if __name__ == '__main__':
 # Pipe()方法返回一对连接对象
 w_conn, r_conn = Pipe()
 wp = Process(target=write, args=(w_conn,))
 rp = Process(target=read, args=(r_conn,))
 wp.start()
 rp.start()
# 执行结果
# [42, None, 'hello']

from multiprocessing import Process, Lock
import time
def print_with_lock(l, i):
 l.acquire()
 try:
  time.sleep(1)
  print('hello world', i)
 finally:
  l.release()
def print_without_lock(i):
 time.sleep(1)
 print('hello world', i)
if __name__ == '__main__':
 lock = Lock()
 # 先执行有锁的
 for num in range(5):
  Process(target=print_with_lock, args=(lock, num)).start()
 # 再执行无锁的
 # for num in range(5):
 #  Process(target=print_without_lock, args=(num,)).start()