Hi,
I am teaching an Python object-oriented programming class based on my own
materials. I am using Pygame to explain many OOP concepts. So far its going
very well.
I have built many small games as examples, but I keep running into a design
dilemma. I will often have a class, where I have an instance variable (I know
it should be called an attribute!), and I want to be able to give it a starting
value, but I also want to be able to reset it to the same value if the game is
played more than once. As a trivial example, here is the start of a Game
class, that keeps track of the score of the game:
class Game:
def __init__(self):
self.score = 0
def reset(self):
self.score = 0
My main code instantiates a Game object and the game plays. If the user wants
to start the game over, I call the reset method. There are two different
problems with this approach:
1) I am duplicating code. This gets nasty when I have lots of instance
variables to reset.
2) Any time I want to change the "starting" value, I must make the identical
change in both methods.
The obvious solution is to have the __init__ method call the reset method:
class Game:
def __init__(self):
self.reset()
def reset(self):
self.score = 0
That does work fine and I like it. But it breaks a general rule that you
should declare all instance variables in the __init__ method. I use PyCharm
for the development of these games, and the "linter" (over the right side
scroll bar) always flags this as a warning that a variable like this is not
defined in my __init__ method.
I'm looking for a general solution that solves this. The best I've come up
with so far is to do something like this for each instance variable:
class Game:
def __init__(self):
self.score = None # create the variable here, but only assign it a
value in the reset method below
self.reset()
def reset(self):
self.score = 0 # Supply the actual start value here.
Anyone have any other suggestions for how to do this cleanly?
Thanks,
Irv
