What is a Functor in Python?

I am new to Python. Can someone explain where the functor value is coming from. Functor = msg.functor, but there is no explanation for the word functor, I've tried googling it and came up with nothing. Also the .val keyword isn't explained anywhere, I'm probably being dim but i cannot find any examples.

def process_action(self, msg, sender):  
    assert msg.get_type() == pedroclient.PObject.structtype
    functor = msg.functor
    assert functor.get_type() == pedroclient.PObject.atomtype
    cmd_type = functor.val
    cmd = msg.args[0]
    if cmd_type == 'stop_':
        assert cmd.get_type() == pedroclient.PObject.structtype
        cmd_functor = cmd.functor.val
        #if cmd_functor in ['pickup', 'putdown']:
        self.stop_arm(cmd.args[0].val)
        #else:
        #    self.stop_arm(cmd.args[0].val)

    elif cmd_type in ['start_', 'mod_']:
        self.start_animate()
        assert cmd.get_type() == pedroclient.PObject.structtype
        cmd_functor = cmd.functor.val
        if cmd_functor == 'pickup':
            self.pickup(cmd.args[0].val, cmd.args[1].val, sender)
        elif cmd_functor == 'putdown':
            if cmd.args[1].get_type() == pedroclient.PObject.inttype:
                self.putdown_on_block(cmd.args[0].val, cmd.args[1].val, 
                                      sender)
            else:
                self.putdown_on_table(cmd.args[0].val, cmd.args[1].val, 
                                      sender)
        elif cmd_functor == 'go_home':
             self.go_home(cmd.args[0].val)

Edit: Sorry there is a lot more code, I have skimmed it as much as i could.

def process_msg(self, term):
    msg = term.args[2]
    sender_process = term.args[1].args[0].args[1].val
    robotID = int(sender_process[-1])-1
    #print msg
    if str(msg) == "initialise_":
        robotID = int(sender_process[-1])-1

def data_cb(self, event):
    self.env.process_msg(event.notification)

The best I can understand it is that the functor is an attribute of msg, which in turn is the argument of system input, where system input is a event notification. Am i correct or completely going of in the wrong direction.

Solution

Basic stuff - msg & functor might be in these places:

Defined in this file
In a local module that is imported by the import statements at the top of this file, this would be a .py file in the directory structure of the app
In an installed package from someone else

.val - this is most likely an attribute containing data. It is not a Python keyword of any kind that I can find. I'm sure you thought that it is probably short for "value". It is either defined in the objects it is a part of (functor, cmd.args[]) or in some superior object that they import and thus inherit val from.