python的multiprocessing

a13698822086

　　创建多个进程

import multiprocessing
from multiprocessing import Process, Lock
import logging
import os
logger = multiprocessing.log_to_stderr() #打印日志
logger.setLevel(multiprocessing.SUBWARNING)
thread_count = 5
def worker(lock,i):
lock.acquire()
print str(i)+aaa
print('module name:', __name__)
if hasattr(os, 'getppid'):  # only available on Unix
print('parent process:', os.getppid())
print('process id:', os.getpid())
logger.warning('doomed')
lock.release()
if __name__ == '__main__':
lock = Lock()
for i in range(thread_count):
Process(target=worker, args=(lock,i,)).start()

　　multiprocessing 提供 Queue 与 Pipe两种方式传输数据

#Queue
from multiprocessing import Process, Queue
def f(q):
q.put([42, None, 'hello'])
if __name__ == '__main__':
q = Queue()
p = Process(target=f, args=(q,))
p.start()
print(q.get())    # prints "[42, None, 'hello']"
p.join()

#Pipe
from multiprocessing import Process, Pipe
def f(conn):
conn.send([42, None, 'hello'])
conn.close()
if __name__ == '__main__':
parent_conn, child_conn = Pipe()
p = Process(target=f, args=(child_conn,))
p.start()
print(parent_conn.recv())   # prints "[42, None, 'hello']"
p.join()

　　共享内存传递数据结果,Value和Array都是线程安全    

from multiprocessing import Process, Value, Array
def f(n, a):
n.value = 3.1415927
for i in range(len(a)):
a = -a
if __name__ == '__main__':
num = Value('d', 0.0)
arr = Array('i', range(10))
print(num.value) # 0.0
print(arr[:])    # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
p = Process(target=f, args=(num, arr))
p.start()
p.join()
print(num.value) # 3.1415927
print(arr[:])    # [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]

　　进程池

import multiprocessing
import time
def do_calculation(data):
print(multiprocessing.current_process().name + " " + str(data))
time.sleep(3)
return data * 2
def start_process():
print ('Starting', multiprocessing.current_process().name)
if __name__ == '__main__':
inputs = list(range(10))
print ('Input   :' + str(inputs))
pool_size = multiprocessing.cpu_count()
pool = multiprocessing.Pool(processes=pool_size,
initializer=start_process,
)
pool_outputs = pool.map(do_calculation, inputs)
pool.close() # no more tasks
pool.join()  # wrap up current tasks
print ('Pool    :' + str(pool_outputs))

　　输出如下

root:~ # python f.py
Input   :[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
('Starting', 'PoolWorker-1')
PoolWorker-1 0
('Starting', 'PoolWorker-2')
PoolWorker-2 2
PoolWorker-1 1
PoolWorker-2 3
PoolWorker-1 4
PoolWorker-2 6
PoolWorker-1 5
PoolWorker-2 7
PoolWorker-1 8
PoolWorker-1 9
Pool    :[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]