I am building some classes for use in future curriculum. I am using PyCharm
for my development. On the right hand edge of the PyCharm editor window, you
get some little bars indicating warnings or errors in your code. I like this
feature and try to clean up as many of those as I can. However, there is one
warning that I am seeing often, and I'm not sure about how to handle it. The
warning I see is:
"Instance attribute <instance variable name> defined outside of __init__ ... "
The following is a simple example. I am creating a card class that I am using
to build card games with PyGame.
class Card():
BACK_OF_CARD_IMAGE = pygame.image.load('images/backOfCard.png')
def __init__(self, window, name, suit, value):
self.window = window
self.suit = suit
self.cardName = name + ' of ' + suit
self.value = value
fileName = 'images/' + self.cardName + '.png'
self.image = pygame.image.load(fileName)
self.backOfCardImage = Card.BACK_OF_CARD_IMAGE
self.conceal()
def conceal(self):
self.faceUp = False
def reveal(self):
self.faceUp = True
<more code snipped>
In this class, I get warnings on the single lines of the conceal and reveal
methods. Yes, the warnings are correct, the variable "self.faceUp" is not
defined inside the __init__ method. My __init__ method calls self.conceal
which is a more logical place to initialize this variable.
My question is, what is the Pythonic way to handle this? In the research that
I have done, I see split results. Some people say that this type of thing is
fine and these warnings should just be ignored. While others say that all
instance variables should be defined in the __init__ method. I like that idea
(and have done so in other languages), but if I define this variable there,
what value should I give it? Do I redundantly set it to the proper starting
value (in case False), or do as others have suggested, set it to None (which
seems a little odd for something that I will use as a Boolean).
I have many more similar cases. For example, in many small game programs, at
the end of my __init__ method, I call a "reset" method in the same class which
initializes a bunch of instance variables for playing a game. When the game is
over, if the user wants to play again, I call the same reset method. Very
clean, and works very well, but all the instance variables defined in that
reset method gets the same warning messages.
Thanks,
Irv
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