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Threading Decorator [Python]


i'm trying to create a simple program using python socket and threading library. I would like to automatize the following procedure using a decorator:

t = threading.Thread(target=function, args=(arg1, arg2))
t.start()

the program is structured using OOP so I defined a subclass inside the main one to contain all the decorators (I've read about this method in this article: https://medium.com/@vadimpushtaev/decorator-inside-python-class-1e74d23107f6). Therefore I have a situation like this:

class Server(object):

    class Decorators(object):

        @classmethod
        def threaded_decorator(cls, function):
            def inner_function():
                function_thread = threading.Thread(target=function)
                function_thread.start()
            return inner_function

    def __init__(self, other_arguments):
        # other code
        pass

    @Decorators.threaded_decorator
    def function_to_be_threaded(self):
        # other code
        pass

But when I try to run, I get the following error: TypeError: function_to_be_threaded() missing one required argument: 'self'. I suspect that the issue is located in the part when I call the threading.Thread(target=function) which somehow doesn't pass the entire function self.function_to_be_threaded. Hence, if you know how to fix this, please can you tell me?. Also, can you tell me if there is a way to implement a decorator that accepts argument which will pass to the Thread class as args=(arguments_of_the_decorator)?

Thank very much you for your time and excuse my English, I'm still practising it


Solution

  • Use *args syntax to move the arguments.In other words, use *args to collect all the positional arguments as a tuple and move it threading.Thread as args.

    import threading
    import time
    class Server(object):
    
        class Decorators(object):
    
            @classmethod
            def threaded_decorator(cls, function):
                def inner_function(*args):
                    function_thread = threading.Thread(target=function,args=args)
                    function_thread.start()
                return inner_function
    
        def __init__(self, count,sleep):
            self.count = count
            self.sleep = sleep
    
        @Decorators.threaded_decorator
        def function_to_be_threaded(self,id):
            for xx in range(self.count):
                time.sleep(self.sleep)
                print("{} ==> {}".format(id,xx))
               
    

    >>> Server(6,1).function_to_be_threaded('a')
    >>> Server(2,3).function_to_be_threaded('b')
    
    a ==> 0
    a ==> 1
    a ==> 2
    b ==> 0
    a ==> 3
    a ==> 4
    a ==> 5
    b ==> 1
    

    see also How can I pass arguments from one function to another?