Question

I have a python program with 2 threads ( let’s name them ‘source’ and ‘destination’ ). Source thread sometimes post a message to destination thread with some arguments. Than destination thread picks a message it must call a corresponding function with aruments saved in message.

This task can be solved multiple ways. The easy one is tu put a big ‘if…if..if’ in destination thread’s message pick cycle and call function according to received message type and saved arguments. But this will result in huge amounf of code ( or big lookup table ) and adding new messages / handler function will evolve additonal step to write code in message pick cycle.

Since python treats functions as first-class objects and have tuples, i want to put a function and argumens inside a message, so than destination thread picks a message it just call a functon saved within a message without any knowledge what function it is.

I can write a code for a functions with specified number of arguments:

from Queue import * from thread import * from time import *  q = Queue()  def HandleMsg( arg1, arg2 ) :   print arg1, arg2  def HandleAnotherMsg( arg1, arg2, arg3 ) :   print arg1, arg2, arg3  def DestinationThread( a ) :   while True :     (f, a, b) = q.get()     f( a, b )  start_new_thread( DestinationThread, ( 0, ) ) print 'start' sleep( 1 ) q.put( (HandleMsg, 1, 2) ) sleep( 1 ) print 'stop' 

The question is: how to modify a code so i can put() a function with any number of arguments in queue? for example HandleAnotherMsg() ? Using q.put( (HandleAnotherMsg, 1, 2, 3) ) will rise a compilation error 🙁

Answer 1

So simple:

def DestinationThread( a ) :   while True :     items = q.get()     func = items[0]     args = items[1:]     func(*args)