Two functions in parallel with multiple arguments and return values
First of all, Process, Pool and Queue all have different use case.
Process is used to spawn a process by creating the Process object.
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()
Pool is used to parallelize execution of function across multiple input values.
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]
Queue is used to communicate between processes.
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
Now, for your case you can use Process & Queue(3rd method) or you can manipulate the pool method to work (below)
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]
Hope this helps.