>>> Further to my questions about overriding builtin methods earlier, how >>> would I make a class able to be accessed and changed using index >>> notation? For example, take the following: >>> deck=CardPile(52) #creates a new deck of cards >>> print(len(deck)) #prints 52, thanks to my __len__ function >>> for c in deck: print c #also works thanks to __iter__ >>> print(deck[4]) #fails with a list index out of range error >>> How would I get the last one working? I tried __getattr__(self, i), >>> but it did not work. I want to be able to get an arbitrary item from >>> the "pile" of cards (which can be a deck, a hand, whatever), and/or >>> set an element. A "pile" is just a list of Card objects, so I would >>> only need to use sequence indexing, not mapping functions. >>> >> >> Implement __getitem__(self, key) (See >> http://docs.python.org/reference/datamodel.html#emulating-container-types ) >> >> If you want to support slicing (access like deck[0:10]), you'll need to >> handle getting a slice object as the key in addition to accepting an integer >> key. >> >> If a pile is really "just" a list of cards, you may want to look into >> inheriting from list instead of re-implementing all of the functionality on >> your own. > I tried this first, by typing > class Pile(list): > Doing this does not seem to work, though, since creating a pile of > size 52 results in a list of size 0, unless I include the __len__ > function. I thought putting (list) in my class definition would > automatically give me the functions of a list as well as anything I > wanted to implement, but that does not seem to be the case.
That depends how you create the Pile of 52 cards: list(52) also doesn't generate 52 (random) items. If you override __init__ to accept an integer that generates the cards for you, this should work. Something like: class Pile(list): def __init__(self, *args, **kwargs): if len(args) == 1 and isinstance(args[0], (int, long)): args = ([Card(i) for i in xrange(args[0])],) super(Pile, self).__init__(*args, **kwargs) allows things like Pile(52), Pile([card1, card2, card3]), Pile(12)[0:3] etc. Cheers, Evert _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor