两个函数并行多个参数和返回值

Question

我有两个独立的功能.每个都需要很长时间才能执行.

def function1(arg):
     do_some_stuff_here
     return result1

def function2(arg1, arg2, arg3):
     do_some_stuff_here
     return result2

我想并行启动它们,得到它们的结果(知道哪个是哪个)并在之后处理结果.根据我的理解,多处理比Python 2.7中的线程(GIL相关问题)更有效.但是我有点迷失是否更好地使用Process,Pool或Queue以及如何以正确的pythonic方式为我的用例实现它们.

任何帮助赞赏;)

Answer 1

首先,Process,Pool和Queue都有不同的用例.

Process用于通过创建Process对象来生成进程.

from multiprocessing import Process

def method1():
    print "in method1"
    print "in method1"

def method2():
    print "in method2"
    print "in method2"

p1 = Process(target=method1) # create a process object p1
p1.start()                   # starts the process p1
p2 = Process(target=method2)
p2.start()

池用于并行化多个输入值的函数执行.

from multiprocessing import Pool

def method1(x):
    print x
    print x**2
    return x**2

p = Pool(3)
result = p.map(method1, [1,4,9]) 
print result          # prints [1, 16, 81]

队列用于在进程之间进行通信.

from multiprocessing import Process, Queue

def method1(x, l1):
    print "in method1"
    print "in method1"
    l1.put(x**2)
    return x

def method2(x, l2):
    print "in method2"
    print "in method2"
    l2.put(x**3)
    return x

l1 = Queue()
p1 = Process(target=method1, args=(4, l1, ))  
l2 = Queue()
p2 = Process(target=method2, args=(2, l2, )) 
p1.start()   
p2.start()      
print l1.get()          # prints 16
print l2.get()          # prints 8

现在,对于您的情况,您可以使用Process&Queue(第三种方法)或者您可以操作池方法(下面)

import itertools
from multiprocessing import Pool
import sys

def method1(x):         
    print x
    print x**2
    return x**2

def method2(x):        
    print x
    print x**3
    return x**3

def unzip_func(a, b):  
    return a, b    

def distributor(option_args):
    option, args = unzip_func(*option_args)    # unzip option and args 

    attr_name = "method" + str(option)            
    # creating attr_name depending on option argument

    value = getattr(sys.modules[__name__], attr_name)(args) 
    # call the function with name 'attr_name' with argument args

    return value


option_list = [1,2]      # for selecting the method number
args_list = [4,2]        
# list of arg for the corresponding method, (argument 4 is for method1)

p = Pool(3)              # creating pool of 3 processes

result = p.map(distributor, itertools.izip(option_list, args_list)) 
# calling the distributor function with args zipped as (option1, arg1), (option2, arg2) by itertools package
print result             # prints [16,8]

希望这可以帮助.