Check for duplicate instances of class by their attributes

Question

I'm writing an engine that creates poker hands, and I'd like each hand to contain only unique cards even though I'm drawing from multiple decks

My problem is, this code

for z in range(dr):
    if self.cards[-1] not in drawcards:
        drawcards[z] = self.cards.pop()

does not register a card with suit x and value y as being equal to another card with suit x and value y

this is my card class:

class Card:
    """A class containing the value and suit for each card"""
    def __init__ (self, value, suit):
        self.value = value
        self.suit = suit
        self.vname = value_names[value]
        self.sname = suit_names[suit]

    def __str__(self):
        #Irrelevant

    def __repr__(self):
        #Irrelevant

how can I make my program register card a with suit x and value y as equal to card b with suit x and value y?

Edit: For people looking at this question in the future, in addition to __eq__,

def __hash__(self):
        return hash((self.value, self.suit))

is necessary for the equality specified in the for loop to work

score 1 · Accepted Answer · edited Mar 22 '19 at 21:05

1

You need to define __eq__ on your class to handle the comparisons. Here are the docs. You'll likely also want to implement __hash__ as well. The docs talk more about that.

def __eq__(self, other):
    # Protect against comparisons of other classes.
    if not isinstance(other, __class__):
        return NotImplemented

    return self.value == other.value and self.suit == other.suit

edited Mar 22 '19 at 21:05

Aran-Fey

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answered Mar 22 '19 at 20:40

schillingt

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2

Remember that `other` can be of any type. – cglacet Mar 22 '19 at 20:41
Thanks @cglacet, I edited my answer to account for that. – schillingt Mar 22 '19 at 20:43
This `__eq__` implementation is majorly broken. I'll take the liberty to fix it. – Aran-Fey Mar 22 '19 at 21:04
1

@Aran-Fey it would be more helpful to me (and likely others) to explain why your suggestions are preferred rather than come across condescending. – schillingt Mar 22 '19 at 21:16
I don't think your edit was warranted. If you plan on inheriting from this class you will need to make a decision on whether to use `self.__class__` or `__class__`. Using `__class__` will still resolve back to the parent class in subclasses while `self.__class__` will be the class that was instantiated. Then the difference between return False or raising NotImplemented is again personal preference based on the scenario. – schillingt Mar 22 '19 at 21:21
Well, feel free to roll back. – Aran-Fey Mar 22 '19 at 21:22

Check for duplicate instances of class by their attributes

1 Answers1