python：在模块之间设置属性

Question

Im teaching myself python and I've come upon a snag in a simple game project I'm working on.

I would like to keep the players stats in a different module from the rooms that are being run by the game engine. Problem is when I try to set a Player attribute from a different module, it doesn't save the new attribute and instantiates the original attribute.

here is the Player class in the entities module

class Player(object):

    def __init__(self):

        self.name = ' '
        self.hp = 0
        self.current_hp = 0
        self.strength = 0
        self.dexterity = 0
        self.constitution = 0

And here is how im trying to manipulate and test the attributes in the rooms module

class CharacterCreation(Scene):
    def enter(self):
        character = entities.Player()
        character.hp = 10
        print character.hp
        return 'barracks'

class Barracks(Scene):
    def enter(self):
        character = entities.Player()
        print character.hp
        return 'shop'

When I test this with the rest of my code, here is what I get.

-------------------------------------------------------------------------------


10
-------------------------------------------------------------------------------


0
-------------------------------------------------------------------------------

So what am I missing here? I thought I could set that attribute using = but it seems I'm mistaken? the first time I did it, it worked, but then how do i get python to set the new value of hp to 10?

Answer 1

You're creating a new Player object in each scene, changing its attributes, and then throwing it away .

You should be explicitly passing one single player into each scene:

def enter(self, player):
   ... do something with player ...

Answer 2

It looks like you're creating a new Player instance on every enter method...

If you're going to have only one player in the game, you could have it as a global variable (usually not very good idea) or even better, as a singleton class: http://blog.amir.rachum.com/post/21850841339/implementing-the-singleton-pattern-in-python

I made some tweakings to the code. It adds the PlayerPool class (which is more like a cache, actually). It may give you some ideas :)

#!/usr/bin/env python
#http://stackoverflow.com/questions/14629710/python-setting-attributes-from-module-to-module/14629838#14629838

class Player(object):
    def __init__(self):
        self.name = ' '
        self.hp = 0
        self.current_hp = 0
        self.strength = 0
        self.dexterity = 0
        self.constitution = 0

class PlayerPool(object):
    _players = dict()

    @classmethod
    def getPlayerByName(cls, name):
        if not name in cls._players:
            newPlayer = Player()
            newPlayer.name = name
            cls._players[newPlayer.name] = newPlayer
        return cls._players[name]


class Scene(object):
    pass

class CharacterCreation(Scene):
    def enter(self):
        character = PlayerPool.getPlayerByName("foobar-hero")
        character.hp = 10
        print "%s has %s points of hp" % (character.name, character.hp)
        return 'barracks'

class Barracks(Scene):
    def enter(self):
        character = PlayerPool.getPlayerByName("foobar-hero")
        print "%s has %s points of hp" % (character.name, character.hp)
        return 'shop'

if __name__ == "__main__":
    step1 = CharacterCreation()
    if step1.enter() == "barracks":
        step2 = Barracks()
        step2.enter()

That outputs:

borrajax@borrajax-comp:~/Tests/Python/Stack Overflow$ python ./players.py 
foobar-hero has 10 points of hp
foobar-hero has 10 points of hp

Welcome to python. I'm sure you'll find it has really cool features... such as the ability to return functions, or pass functions as parameters, inspect the classes defined in any module... Looks like things you could find useful.