总结

关于GIL

GIL, is a mutex that protects access to Python objects, preventing multiple threads from executing Python bytecodes at once — Python Wiki

为何需要GIL? 因为Python解释器不是线程安全的。

代码示例

多进程用法：

# create a process
process = multiprocessing.Process(target=task)
# create a process
process = multiprocessing.Process(target=task, args=(arg1, arg2))
# run the new process
process.start()# SuperFastPython.com
# example of running a function in another process
from time import sleep
from multiprocessing import Process# a custom function that blocks for a moment
def task():# block for a momentsleep(1)# display a messageprint('This is from another process')# entry point
if __name__ == '__main__':# create a processprocess = Process(target=task)# run the processprocess.start()# wait for the process to finishprint('Waiting for the process...')process.join()

多进程之间采用队列通信:

from concurrent.futures import ThreadPoolExecutor, wait, ALL_COMPLETED, as_completed
if __name__ == '__main__':print('main thread is {}'.format(threading.current_thread().name))start_time = time.time()### multithread queuefrom queue import Queuequeue = Queue()tw = threading.Thread(target=write_to_queue, args=(queue,))tr = threading.Thread(target=read_from_queue, args=(queue,))tr.setDaemon(True)tw.start()tr.start()tw.join()end_time = time.time()print('total time is {}'.format(str(end_time - start_time)))

多线程之间通信:

def increase(var, lock):global total_increase_timesfor i in range(1000000):if lock.acquire():var[0] += 1lock.release()total_increase_times += 1def decrease(var, lock):global total_decrease_timesfor i in range(1000000):if lock.acquire():var[0] -= 1lock.release()total_decrease_times += 1if __name__ == '__main__':print('main thread is {}'.format(threading.current_thread().name))start_time = time.time()lock = threading.Lock()var = [5]total_increase_times = 0total_decrease_times = 0t1 = threading.Thread(target=increase, args=(var, lock))t2 = threading.Thread(target=decrease, args=(var, lock))t1.start()t2.start()t1.join()t2.join()print(var)print('total increase times: {}'.format(str(total_increase_times)))print('total decrease times: {}'.format(str(total_decrease_times)))end_time = time.time()print('total time is {}'.format(str(end_time - start_time)))