Python并發(fā)(多線程)

并發(fā)性常常被誤解為并行性。 并發(fā)意味著調(diào)度獨(dú)立代碼以系統(tǒng)方式執(zhí)行。 本章重點(diǎn)介紹使用Python的操作系統(tǒng)的并發(fā)執(zhí)行。

以下程序?qū)崿F(xiàn)執(zhí)行操作系統(tǒng)的并發(fā)性 -

import os
import time
import threading
import multiprocessing

NUM_WORKERS = 4

def only_sleep():
   print("PID: %s, Process Name: %s, Thread Name: %s" % (
      os.getpid(),
      multiprocessing.current_process().name,
      threading.current_thread().name)
   )
   time.sleep(1)

def crunch_numbers():
   print("PID: %s, Process Name: %s, Thread Name: %s" % (
      os.getpid(),
      multiprocessing.current_process().name,
      threading.current_thread().name)
   )
   x = 0
   while x < 10000000:
      x += 1
for _ in range(NUM_WORKERS):
   only_sleep()
end_time = time.time()
print("Serial time=", end_time - start_time)

# Run tasks using threads
start_time = time.time()
threads = [threading.Thread(target=only_sleep) for _ in range(NUM_WORKERS)]
[thread.start() for thread in threads]
[thread.join() for thread in threads]
end_time = time.time()

print("Threads time=", end_time - start_time)

# Run tasks using processes
start_time = time.time()
processes = [multiprocessing.Process(target=only_sleep()) for _ in range(NUM_WORKERS)]
[process.start() for process in processes]
[process.join() for process in processes]
end_time = time.time()

print("Parallel time=", end_time - start_time)

執(zhí)行上述程序生成以下輸出 -

說(shuō)明
multiprocessing是一個(gè)類似于線程模塊的包。 該軟件包支持本地和遠(yuǎn)程并發(fā)。 由于這個(gè)模塊，程序員可以在給定的系統(tǒng)上使用多個(gè)進(jìn)程。