如何在不实例化类的情况下从另一个文件中读取实例变量？

Question

I'm relatively new to Python and I'm having some trouble importing a variable to use it in another class. I did look at several other questions on this topic and tried to make it work, but it seems the way I set up this program early on might be the problem. I'll simplify what's going on so there's less to read...

Server.py:

import Game
class Server():
    def __init__(self):
        # Server connection details here
        self.test = 5
        self.game = Game()

    def serve(self):
        # Client processing, etc.
        self.game.game_loop()

if __name__ == "__main__":
    server = Server()
    server.serve()

Game.py:

class Game():
    def __init__(self):
        # Other variables...

    def game_loop(self):
        # To reference server's instance variables
        from Server import server

        print test

In this example, I'm trying to reference the variable "test" from the server instance of Server. It's worth noting that this DOES WORK if I put both classes in the same file and then remove the if statement at the end of it...but I'd rather not have one file that long :)

Since these are in separate files, I can't get the instance variables from "server" without removing that if statement in Server.py. When I do remove it, I get socket errors because of other stuff I'm doing...I need to make it so that there's only ever one server object (and that its class is only "called" once), but it'd be really handy to be able to reference those instance variables without passing them in to my Game class every time it runs...

Part of this is definitely my fault in that I set my program up wrong...but I'm too far in to start that over. Is there any way I can take this sort of setup and read in those variables?

Answer 1

First, test exists as an instance variable, so you'll need to pass an instance of Server to your game loop:

class Server:
  def serve(self):
    # Client processing, etc.
    self.game.game_loop(self)

Next, you can find test in game_loop by looking in the passed-in instance:

class Game:
  def game_loop(self, server):
    print server.test