Python is calling the base class instead of the derived class

Question

I am new to python. I am trying to implement the most basic version of a reflex agent in Python. A lot of the code, in fact, pretty much all of it has been copied from the repo that it came from. I am trying to trim it down to understand it better but there seems to be a problem with the code.

import collections
import collections.abc
import numbers
import random


class Thing:
    def __repr__(self):
        return '<{}>'.format(getattr(self, '__name__', self.__class__.__name__))

    def is_alive(self):
        return hasattr(self, 'alive') and self.alive

    def show_state(self):
        print("I don't know how to show_state.")


class Agent(Thing):
    def __init__(self, program=None):
        self.alive = True
        self.bump = False
        self.holding = []
        self.performance = 0
        if program is None or not isinstance(program, collections.abc.Callable):
            print("Can't find a valid program for {}, falling back to default.".format(self.__class__.__name__))

            def program(percept):
                return eval(input('Percept={}; action? '.format(percept)))

        self.program = program

    def can_grab(self, thing):
        """Return True if this agent can grab this thing.
        Override for appropriate subclasses of Agent and Thing."""
        return False

loc_A, loc_B = (0, 0), (1, 0)

def ReflexVacuumAgent():
    def program(percept):
        print("calling correct")
        ## ---------------------------
        ## here is the issue
        ## ---------------------------
        location, status = percept
        if status == 'Dirty':
            return 'Suck'
        elif location == loc_A:
            return 'Right'
        elif location == loc_B:
            return 'Left'

    return Agent(program)


class Environment:
    def __init__(self):
        self.things = []
        self.agents = []

    def thing_classes(self  ):
        return []  # List of classes that can go into environment

    def percept(self, agent):
        """Return the percept that the agent sees at this point. (Implement this.)"""
        raise NotImplementedError

    def default_location(self, thing):
        """Default location to place a new thing with unspecified location."""
        return None

    def is_done(self):
        """By default, we're done when we can't find a live agent."""
        return not any(agent.is_alive() for agent in self.agents)

    def step(self):
        """Run the environment for one time step. If the
        actions and exogenous changes are independent, this method will
        do. If there are interactions between them, you'll need to
        override this method."""
        if not self.is_done():
            actions = []
            for agent in self.agents:
                if agent.alive:
                    actions.append(agent.program(self.percept(agent)))
                else:
                    actions.append("")
            for (agent, action) in zip(self.agents, actions):
                self.execute_action(agent, action)
            self.exogenous_change()

    def add_thing(self, thing, location=None):
        """Add a thing to the environment, setting its location. For
        convenience, if thing is an agent program we make a new agent
        for it. (Shouldn't need to override this.)"""
        if not isinstance(thing, Thing):
            thing = Agent(thing)
        if thing in self.things:
            print("Can't add the same thing twice")
        else:
            thing.location = location if location is not None else self.default_location(thing)
            self.things.append(thing)
            if isinstance(thing, Agent):
                thing.performance = 0
                self.agents.append(thing)


class Dirt(Thing):
    pass


class TrivialVacuumEnvironment(Environment):
    def __init__(self):
        super().__init__()
        self.status = {loc_A: random.choice(['Clean', 'Dirty']),
                       loc_B: random.choice(['Clean', 'Dirty'])}

    def percept(self, agent):
        return self.status[agent.location]

    def thing_classes(self):
        return [Dirt, ReflexVacuumAgent]




# instantiate trivial environment 
env = TrivialVacuumEnvironment()
# instantiate trivial agent
agnt = ReflexVacuumAgent()
# add agent to environment
env.add_thing(agnt, location=loc_A)
# step forward
env.step() 

I have highlighted what I have found via debugging. Unfortunately I don't have the python skills to do anything about it.

The error I am getting is as follows

Traceback (most recent call last):
  File "/home/anthonygoddard962/git/agents/environment.py", line 137, in <module>
    env.step() 
  File "/home/anthonygoddard962/git/agents/environment.py", line 88, in step
    actions.append(agent.program(self.percept(agent)))
  File "/home/anthonygoddard962/git/agents/environment.py", line 45, in program
    location, status = percept
ValueError: too many values to unpack (expected 2)

Answer 1

After fixing some school boy errors with python I have some working code. The compiling code is below.

import collections
import collections.abc
import numbers
import random


class Thing:
    def __repr__(self):
        return '<{}>'.format(getattr(self, '__name__', self.__class__.__name__))

    def is_alive(self):
        return hasattr(self, 'alive') and self.alive

    def show_state(self):
        print("I don't know how to show_state.")


class Agent(Thing):
    def __init__(self, program=None):
        self.alive = True
        self.bump = False
        self.holding = []
        self.performance = 0
        if program is None or not isinstance(program, collections.abc.Callable):
            print("Can't find a valid program for {}, falling back to default.".format(self.__class__.__name__))

            def program(percept):
                return eval(input('Percept={}; action? '.format(percept)))

        self.program = program

    def can_grab(self, thing):
        """Return True if this agent can grab this thing.
        Override for appropriate subclasses of Agent and Thing."""
        return False

loc_A, loc_B = (0, 0), (1, 0)

def ReflexVacuumAgent():
    def program(percept):
        location, status = percept
        if status == 'Dirty':
            return 'Suck'
        elif location == loc_A:
            return 'Right'
        elif location == loc_B:
            return 'Left'
    
    return Agent(program)


class Environment:
    def __init__(self):
        self.things = []
        self.agents = []

    def thing_classes(self  ):
        return []  # List of classes that can go into environment

    def percept(self, agent):
        """Return the percept that the agent sees at this point. (Implement this.)"""
        raise NotImplementedError

    def execute_action(self, agent, action):
        """Change the world to reflect this action. (Implement this.)"""
        raise NotImplementedError

    def default_location(self, thing):
        """Default location to place a new thing with unspecified location."""
        return None

    def is_done(self):
        """By default, we're done when we can't find a live agent."""
        return not any(agent.is_alive() for agent in self.agents)

    def step(self):
        if not self.is_done():
            actions = []
            for agent in self.agents:
                if agent.alive:
                    actions.append(agent.program(self.percept(agent)))
                else:
                    actions.append("")
            for (agent, action) in zip(self.agents, actions):
                self.execute_action(agent, action)

    def add_thing(self, thing, location=None):
        if not isinstance(thing, Thing):
            thing = Agent(thing)
        if thing in self.things:
            print("Can't add the same thing twice")
        else:
            thing.location = location if location is not None else self.default_location(thing)
            self.things.append(thing)
            if isinstance(thing, Agent):
                thing.performance = 0
                self.agents.append(thing)


class Dirt(Thing):
    pass


class TrivialVacuumEnvironment(Environment):
    def __init__(self):
        super().__init__()
        self.status = {loc_A: random.choice(['Clean', 'Dirty']),
                       loc_B: random.choice(['Clean', 'Dirty'])}

    def percept(self, agent):
        return agent.location, self.status[agent.location]

    def execute_action(self, agent, action):
        if(action == 'Right'):
            agent.location = (1, 0)
        if(action == 'Left'):
            agent.location = (0, 0)
        if(action == 'Suck'):
            self.status[agent.location] = 'Clean'

    def show_status(self):
        print(self.status)

    def thing_classes(self):
        return [Dirt, ReflexVacuumAgent]




# instantiate trivial environment 
env = TrivialVacuumEnvironment()
# instantiate trivial agent
agnt = ReflexVacuumAgent()
# add agent to environment
env.add_thing(agnt, location=loc_A)
env.show_status()
print(agnt.location)
# step forward and show status
env.step() 
env.show_status()
print(agnt.location)
# ...and again
env.step() 
env.show_status()
print(agnt.location)
# ...and again
env.step() 
env.show_status()
print(agnt.location)