在这种情况下如何在Python中使用多处理？

Question

I try to use simple way to make mulitiprocessing:

urls = [1, 2, 3, 4]
p = Pool(2)
p.map(open, urls)

Where open() is function, that does calculations.

def open(url):
    print(url)

When I do print(url) it returns me strange result:

1
2
3
4
1
2
3
4

I can assume that each of process Pool(2) handler the same calculations there is wrong.

I need that process 1 takes [1, 2] for handling and process 2 takes [3, 4]

Answer 1

I think this should do what you want to:

import multiprocessing
def func(x):
    return x[0] + x[1]

if __name__ == "__main__":    
    p = multiprocessing.Pool(2)
    for x in p.map(func, [(1, 2), (3, 4)]):
        print(x)

output:

 3
 7