Creating a Class Attribute dependent on Another Attribute - python-2.7

Question

I am currently working on a small RPG in Pygame to get used to object oriented coding.
When looking into how to auto-update a property I came across the following:
class P:
def __init__(self,x):
self.x = x
#property
def x(self):
return self.__x
#x.setter
def x(self, x):
if x < 0:
self.__x = 0
elif x > 1000:
self.__x = 1000
else:
self.__x = x
I tried applying it to my code but I get the following error:
File "weapons.py", line 13, in __init__
self.name = '{} {}'.format(ammo, self.raw_name)
TypeError: name() takes exactly 3 arguments (2 given)
I understand what the error is but I don't get how to solve it since I need both the raw_name and the ammo attributes to auto-update my Arrow instance's name.
My class is as such:
class Projectile(Item):
def __init__(self, name, value, image, x, y, speed, dmg, dmg_modif, ammo):
super(Projectile, self).__init__(name, value, image, x, y)
self.dest = (self.rect[0],self.rect[1])
self.speed = speed
self.dmg_modif = dmg_modif
self.dmg = dmg
self.orientation = 0
self.ammo = ammo
#property
def name(self):
return self.___name
#name.setter
def name(self, raw_name, ammo):
if '{} {}'.format(raw_name,ammo) != self.___name:
self.___name = '{} {}'.format(raw_name,ammo)
The child class which returns the error is:
class Arrow(Projectile):
def __init__(self, ammo): #name, value, image, x, y, dmg
self.raw_name = 'Arrows'
self.name = '{} {}'.format(ammo, self.raw_name)
self.value = 5
self.image = variables.quiver_img
self.speed = 4
self.dmg = 2
self.dmg_modif = 1
super(Arrow, self).__init__(self.name, self.value, self.image, 200, 150, self.speed, self.dmg, self.dmg_modif, ammo)
And the parent classes are, Item and MySprite:
class Item(MySprite):
def __init__(self, name, value, image, x, y):
# Call the parent class (Sprite) constructor
super(Item, self).__init__(image, x, y)
self.name = name
self.value = value
self.inv_pos = -1
and
class MySprite(pygame.sprite.Sprite):
def __init__(self,image,x,y):
# Call the parent class (Sprite) constructor
super(MySprite, self).__init__()
self.image = image
self.rect = self.image.get_rect().move(x, y) #initial placement
self.top_cp = (self.rect[0]+self.rect[2]/2,self.rect[1])
self.bot_cp = (self.top_cp[0],self.rect[1]+self.rect[3])
self.left_cp = (self.rect[0],self.rect[1]+self.rect[3]/2)
self.right_cp = (self.left_cp[0]+self.rect[2],self.left_cp[1])
self.center = self.rect.center
self.pos = self.rect.topleft
self.blit_order = 1
self.level = variables.current_level #Level(1)#level to which sprite belongs
Any help would be welcome !

Answer 1

Please provide a minimal example next time.
Your code looks a little complicated. OK, the first problem is that you can't pass multiple arguments to a setter. You can either pass a tuple or just use a traditional setter method def set_name(self, name, ammo):.
Another problem is that you use the ___name attribute before it has been set, for example in the second line of the Arrows __init__ method.
Private attributes should have one underscore not three (that's just a convention to warn other programmers). If you have two or more underscores than the name gets mangled.
Also, it looks to me like you change the name in the setter only if the new name is equal to the old name (kinda pointless ;)). What do you actually want to do there? Maybe you don't need properties at all.
Here's a fixed (minimal) version of your code:
import pygame
class MySprite(pygame.sprite.Sprite):
def __init__(self):
super(MySprite, self).__init__()
class Item(MySprite):
def __init__(self, name):
super(Item, self).__init__()
self.name = name
class Projectile(Item):
def __init__(self, name):
super(Projectile, self).__init__(name)
#property
def name(self):
return self._name
#name.setter
def name(self, name):
self._name = name + ' foo'
class Arrow(Projectile):
def __init__(self):
super(Arrow, self).__init__(name='Arrows')
arrow = Arrow()
print(arrow.name)
arrow.name = 'New name'
print(arrow.name)

Answer 2

So I eventually managed to solve my problem:
class Projectile(object):
def __init__(self, raw_name, ammo):
self.raw_name = raw_name
self.name = self.raw_name
self.ammo = ammo
#property
def ammo(self):
return self._ammo
#ammo.setter
def ammo(self, ammo):
self.name = str(ammo) + self.raw_name
self._ammo = ammo
class Arrow(Projectile):
def __init__(self):
self.raw_name = ' Arrows'
self.name = self.raw_name
super(Arrow, self).__init__(self.raw_name, ammo
= 10)
arrow = Arrow()
print arrow.ammo
print arrow.name
arrow.ammo = 15
print arrow.ammo
print arrow.name
gives:
>>>10
>>>10 Arrows
>>>15
>>>15 Arrows