在Python多处理库中,是否有支持多个参数的pool.map变体?

import multiprocessing

text = "test"

def harvester(text, case):
    X = case[0]
    text + str(X)

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=6)
    case = RAW_DATASET
    pool.map(harvester(text, case), case, 1)
    pool.close()
    pool.join()

当前回答

您可以使用以下两个函数,以避免为每个新函数编写包装器:

import itertools
from multiprocessing import Pool

def universal_worker(input_pair):
    function, args = input_pair
    return function(*args)

def pool_args(function, *args):
    return zip(itertools.repeat(function), zip(*args))

将函数函数与参数arg_0、arg_1和arg_2的列表一起使用,如下所示:

pool = Pool(n_core)
list_model = pool.map(universal_worker, pool_args(function, arg_0, arg_1, arg_2)
pool.close()
pool.join()

其他回答

将Python 3.3+与pool.starmap()一起使用:

from multiprocessing.dummy import Pool as ThreadPool 

def write(i, x):
    print(i, "---", x)

a = ["1","2","3"]
b = ["4","5","6"] 

pool = ThreadPool(2)
pool.starmap(write, zip(a,b)) 
pool.close() 
pool.join()

结果:

1 --- 4
2 --- 5
3 --- 6

如果您喜欢,还可以zip()更多参数:zip(a,b,c,d,e)

如果希望将常量值作为参数传递:

import itertools

zip(itertools.repeat(constant), a)

如果您的函数应该返回以下内容:

results = pool.starmap(write, zip(a,b))

这将提供一个包含返回值的列表。

text = "test"

def unpack(args):
    return args[0](*args[1:])

def harvester(text, case):
    X = case[0]
    text+ str(X)

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=6)
    case = RAW_DATASET
    # args is a list of tuples 
    # with the function to execute as the first item in each tuple
    args = [(harvester, text, c) for c in case]
    # doing it this way, we can pass any function
    # and we don't need to define a wrapper for each different function
    # if we need to use more than one
    pool.map(unpack, args)
    pool.close()
    pool.join()
import time
from multiprocessing import Pool


def f1(args):
    vfirst, vsecond, vthird = args[0] , args[1] , args[2]
    print(f'First Param: {vfirst}, Second value: {vsecond} and finally third value is: {vthird}')
    pass


if __name__ == '__main__':
    p = Pool()
    result = p.map(f1, [['Dog','Cat','Mouse']])
    p.close()
    p.join()
    print(result)

另一个简单的选择是将函数参数包装在元组中,然后包装应该在元组中传递的参数。在处理大量数据时,这可能并不理想。我相信它会为每个元组创建副本。

from multiprocessing import Pool

def f((a,b,c,d)):
    print a,b,c,d
    return a + b + c +d

if __name__ == '__main__':
    p = Pool(10)
    data = [(i+0,i+1,i+2,i+3) for i in xrange(10)]
    print(p.map(f, data))
    p.close()
    p.join()

以某种随机顺序给出输出:

0 1 2 3
1 2 3 4
2 3 4 5
3 4 5 6
4 5 6 7
5 6 7 8
7 8 9 10
6 7 8 9
8 9 10 11
9 10 11 12
[6, 10, 14, 18, 22, 26, 30, 34, 38, 42]

对于Python 2,可以使用此技巧

def fun(a, b):
    return a + b

pool = multiprocessing.Pool(processes=6)
b = 233
pool.map(lambda x:fun(x, b), range(1000))