Python 3: Name 'Class instance' not defined

Question

I've been working on a text-based adventure game and currently I'm working on splitting up one large game script I have into separate modules.

This is the main game module containing the game's logic. Within the main() function I have defined instances of classes

from gameworld import *


def main():

    player = Player("Jeff", 100)
    bag = Bag([])
    location = Location('introd')

    command = '  '
    while command != "":
        command = input('>>> ')
        if command in location.room.exits:
            location.travel(command)
        elif command == 'look':
            location.room_desc()
        elif command == '':
            print('You have to say what it is you want to do!')
            command = '#'
        elif command == 'search':
            location.search_room()
        elif command.split()[0] == 'Take':
            bag.check_take(command.split()[1])
        elif command == 'Inventory':
            bag.check_inv()
        else:
            print('Invalid command')


if __name__ == '__main__':
    main()

Below is an excerpt from the gameworld module. It includes the functions that I'm having difficulty with. The Location.key_check and Bag.check_take functions.

#gameworld.py

class Room:

    def __init__(self, name, description, exits, actions, roominv, roomkey, lock):
        self.name = name
        self.description = description
        self.exits = exits
        self.actions = actions
        self.roominv = roominv
        self.roomkey = roomkey
        self.lock = lock

class Location:

    def __init__(self, room):
        self.room = world[room]

    def key_check(self, new_room_name):
        if world[new_room_name].lock and world[new_room_name].roomkey not in bag.inventory:
            self.no_key()
        else:
            world[new_room_name].lock = False
            self.set_room(new_room_name)
            self.room_desc()
class Bag():

    def __init__(self, inventory):
        self.inventory = inventory

    def add_to_inv(self, key):
        self.inventory.append(location.room.roominv[key])
        del location.room.roominv[key]

    def none_here(self, key):
        print("You can't find a", key)

    def check_take(self, key):
        if location.room.roominv and key in location.room.roominv:
            self.add_to_inv(key)
            print('you take the', key)
        else:
            self.none_here(key)

When I run the game, and attempt to pick up an item, I receive this traceback error:

Traceback (most recent call last):
  File "C:\Users\Daniel\Python 3.6\Scripts\PythonPR\PythonPR\FlubbosModuleTest.py", line 31, in <module>
    main()
  File "C:\Users\Daniel\Python 3.6\Scripts\PythonPR\PythonPR\FlubbosModuleTest.py", line 23, in main
    bag.check_take(command.split()[1])
  File "C:\Users\Daniel\Python 3.6\Scripts\PythonPR\PythonPR\gameworld.py", line 81, in check_take
    if location.room.roominv and key in location.room.roominv:
NameError: name 'location' is not defined

I receive a similar error when attempting to move to a locked room and the key_check method runs. When the code is all contained in the same script, it runs fine with no problem accessing these class instances.

Answer 1

You need to pass the location variable when you are calling bag.check_take as an argument as location is not defined and is not in scope inside the Bag class. You need to pass the variable represent other object when you call a class member function.

Answer 2

In the case that you've designed your Bag to have an inventory attribute which you update.

def add_to_inv(self, key):
   self.inventory.append(location.room.roominv[key])
   del location.room.roominv[key]

Nitpick : move the mutation of the room inventory for a location to a manager function. See rest of answer below to get an idea.

You can make check_take into a function that take a key, bag and location. This function can be imported and passed key, bag and location accordingly.

def check_take(key, bag, location=None):
    if location.room.roominv and key in location.room.roominv:
        bag.add_to_inv(key)
    else:
        bag.none_here(key)