Threading and passing values with **kwargs errors to TypeError

Question

I'm pretty new to Python and was looking into using threading for some code via this post: Python - Using threads or a queue to iterate over a for loop that calls a function

I was wondering why this simple example code errors out to

Error: line 1: TypeError: file <maya console> line 4: __init__() got
an unexpected keyword argument 'A' #

My code:

import threading
class Test(threading.Thread):
    def __init__(self, **kwargs):
        super(Test, self).__init__( **kwargs)
        self.__dict__.update(**kwargs)

A = None
B = 1   
test = Test(A = A, B = B)
print test.A
print test.B

My assumption is it has to do with super(Test, self).__init__( **kwargs) call, but I'm not sure how to work around it. My goal is pass in a rather large amount of arguments which is why I'm using **kwargs to begin with.

Answer 1

threading.Thread.__init__ expects (at most) group, target, name, args, kwargs and verbose keyword arguments.

Since you have a large number of extra arguments (presumably more than the six that threading.Thread.__init__ expects), then it may be less work to explicity extract those six and handle the rest with

self.__dict__.update(**kwargs)

---

import threading

class Test(threading.Thread):
    def __init__(self, **kwargs):
        super(Test, self).__init__(
            **{k: v for k in 'group target name args kwargs verbose'.split()
               if k in kwargs})
        self.__dict__.update(**kwargs)

A = None
B = 1
test = Test(A=A, B=B)
print test.A
print test.B

---

Note, if you call __init__ with no arguments:

super(Test, self).__init__()

then a whole bunch of attributes used by threading.Thread will not be set:

class Thread(_Verbose):    
    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs=None, verbose=None):
        assert group is None, "group argument must be None for now"
        _Verbose.__init__(self, verbose)
        if kwargs is None:
            kwargs = {}
        self.__target = target
        self.__name = str(name or _newname())
        self.__args = args
        self.__kwargs = kwargs
        self.__daemonic = self._set_daemon()
        self.__ident = None
        self.__started = Event()
        self.__stopped = False
        self.__block = Condition(Lock())
        self.__initialized = True
        # sys.stderr is not stored in the class like
        # sys.exc_info since it can be changed between instances
        self.__stderr = _sys.stderr

I don't think that is what you want to happen...

Answer 2

You're passing the arguments A and B to the Thread constructor, which doesn't need them. Probably you should just call the super constructor with no arguments.