How to increment a variable contained within a class in python from outside of its class?

Question

I have a fairly simple python question, as I am pretty new to the language. I started writing a quick program just for practice, but have now become frustrated because I cannot get it to work.

import random import sys class Meta: turncounter = 1 class Enemy: life = 10 wis = 1 str = 3 def heal(self): healscore = self.wis + random.randrange(1, 7, 1) self.life += healscore print "Enemy healed for " + str(healscore) + ".\n" self.checklife() Meta.turncounter += 1 def attack(self, player): damage = self.str + random.randrange(1, 5, 1) player.life -= damage print "You took " + str(damage) + " damage.\n" Player.checklife(player) Meta.turncounter += 1 def checklife(self): if self.life <= 0: print "The enemy is dead.\n" sys.exit(0) else: print "Enemy's HP: " + str(self.life) + ".\n" class Player: life = 50 wis = 3 str = 5 def heal(self): healscore = self.wis + random.randrange(1, 7, 1) self.life += healscore print "You healed for " + str(healscore) + ".\n" Meta.turncounter += 1 def attack(self, enemy): damage = self.str + random.randrange(1, 5, 1) enemy.life -= damage print "You did " + str(damage) + " damage.\n" Enemy.checklife(enemy) Meta.turncounter += 1 def checklife(self): if self.life <= 0: sys.exit("You died!") else: print "HP: " + str(self.life) + ".\n" paladin = Player() hollow = Enemy() turnmeta = Meta.turncounter % 2 move = random.randrange(1, 3, 1) print turnmeta print move while turnmeta == 0: if move == 1 and paladin.life <= 10: paladin.heal() print turnmeta elif move != 0 or (move == 1 and hollow.life > 15): paladin.attack(hollow) print turnmeta while turnmeta > 0: if move == 1 and hollow.life <= 15: print turnmeta elif move != 0 or (move == 1 and hollow.life > 15): hollow.attack(paladin) print turnmeta

As you can see, this program isn't particularly complex; it is just meant to be something to generally understand python syntax and loops and such. For some reason, whenever I run the program, instead of the turncounter incrementing and the paladin / hollow having a back and forth, the turncounter stays locked in at 1, causing the hollow to attack until the paladin dies, instantly ending the program.

Is the indentation correct in your question? The class methods don't appear to be indented. — Brendan Abel
– Brendan Abel, Commented Jun 23, 2016 at 23:56

juanpa.arrivillaga · Accepted Answer · 2016-06-24 00:04:44Z

The problem is your while-loop is relying on turnmeta, which doesn't change when you increment Meta.turncounter in your class methods.

Notice:

>>> class Meta(object): ... turncounter = 0 ... >>> turnmeta = Meta.turncounter >>> turnmeta 0 >>> Meta.turncounter += 1 >>> turnmeta 0 >>> Meta.turncounter 1

Just use Meta.turncounter.

That being said, your design, which relies heavily on class attributes, is not good design, and skimming over your code I don't think you are doing what you think you are doing. Python class definitions are different from Java.

You need to define instance attributes inside of an __init__ method (or any other method) using self.attribute, and not in the class namespace, as you have done in your class definitions.

Read the docs: https://docs.python.org/3.5/tutorial/classes.html

Simon · Accepted Answer · 2016-06-24 00:05:02Z

turnmeta is the result of your calculation Meta.turncounter % 2.

It doesn't make any reference to your Meta.turncounter anymore.

You should reassign the turnmeta after each turns.

Jacques Gaudin · Accepted Answer · 2016-06-24 00:07:49Z

Your second while loop never ends if move == 1 because the value of the variable turnmeta is never changed and is always 1 and the variable 'move` is always 1.

You need to give them a new value in your loops: turnmeta = Meta.turncounter % 2 and move = random.randrange(1, 3, 1) if I understand your program correctly.

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