在程序之間共享狀態
預設情況下,在不同程序中執行的程式碼不共享相同的資料。但是,multiprocessing
模組包含幫助在多個程序之間共享值的原語。
import multiprocessing
plain_num = 0
shared_num = multiprocessing.Value('d', 0)
lock = multiprocessing.Lock()
def increment():
global plain_num
with lock:
# ordinary variable modifications are not visible across processes
plain_num += 1
# multiprocessing.Value modifications are
shared_num.value += 1
ps = [multiprocessing.Process(target=increment) for n in range(4)]
for p in ps:
p.start()
for p in ps:
p.join()
print("plain_num is %d, shared_num is %d" % (plain_num, shared_num.value))
# Out: plain_num is 0, shared_num is 4