具有一个常量参数，一个迭代的ProcessPoolExecutor

Question

我想在Python中使用ProcessPoolExecutor，并为该函数提供一个常量参数和一个可迭代的参数。作为错误消息，我收到“ AttributeError：无法使本地对象'main ..'腌制”。如果我能使该功能正常工作，那就太好了！

import concurrent.futures

PRIMES = ['a','b','c']

def is_prime(_a, n):    
    return (_a, n)

def main():  
    a = '3'  
    with concurrent.futures.ProcessPoolExecutor(max_workers=5) as executor:
        for result in executor.map(lambda x,y: is_prime(a,y), a, PRIMES):
            print('is prime: %s' %result[0])

if __name__ == '__main__':        
    main()

谢谢！