python 3.5的绑定缓冲区（生产者/消费者）

Question

I'm writing the classic producer/consumer problem in Python 3.5 using a deque as buff and 2 process that should work in parallel but unfortunately only the producer works, while the consumer doesn't "consume".. where am I wrong? This is my code:

from time import sleep
import random
from collections import deque
import multiprocessing

MAX_LEN = 10
buff = deque(maxlen=MAX_LEN)

class producer:
    while True:
        if len(buff) == MAX_LEN:
            print("Producer: The buff is full, waiting...")
            sleep(10)
        buff.append(random.randint(1,9))


class consumer:
    while True:
        print("Consumer: hi")
        if len(buff) == 0:
            print("Consumer: The buff is empty, waiting...")
            sleep(10)
        buff.pop()



if __name__ == '__main__':
    multiprocessing.Process(target=producer).start().join()
    multiprocessing.Process(target=consumer).start().join()

and the result of this is:

Producer: The buff is full, waiting...
Producer: The buff is full, waiting...
Producer: The buff is full, waiting...
Producer: The buff is full, waiting...
Producer: The buff is full, waiting...
Producer: The buff is full, waiting...
^CTraceback (most recent call last):
  File "./boundedbuffer.py", line 9, in <module>
    class producer:
  File "./boundedbuffer.py", line 13, in producer
    sleep(10)
KeyboardInterrupt

Just for now I want to implement in this way, as an exercise, just to see if I understand the argument, although I know that it is not the most correct and that I should use semaphores or monitors. Maybe later I will try to implement it differently. Thank you all in advance for your help and good evening :)

Answer 1

You have defined classes with while True: loops in their bodies.

The interpreter will execute the first while loop in your file forever.

multiprocessing.Process expects a callable as its target argument, so if you change the producer and consumer classes to functions the if __ name __ == __ main __ : block will be executed (though you still may not get the outcome that you expect).

def producer():
    while True:
        if len(buff) == MAX_LEN:
            print("Producer: The buff is full, waiting...")
            sleep(10)
        buff.append(random.randint(1,9))


def consumer():
    while True:
        print("Consumer: hi")
        if len(buff) == 0:
            print("Consumer: The buff is empty, waiting...")
            sleep(10)
        buff.pop()