[Tutor] Methods defined in my class are affecting all the objects at runtime.

[Brian Stovall]

Hello world!

I obviously don't understand something important and basic, but I am
having trouble figuring it out myself... I am running python v3.2.2 on
a Win XP machine.

My code:

import card_model
import random

class Pile:
    """An Object reperesenting a list of 'Card' Objects: could be a
hand, discard pile, tableau
    or anything really. Has a display_type that is used to clarify
what kind of display to use, and
    .deal(cards[] , new_pile(Pile Object)) and .shuffle() methods."""

    DISPLAY_TYPES = ["STACK", "FAN", "ACCORDION", "CASCADE"]

    def __init__(self, cards = [], display_type = "STACK"):
        self.cards = cards
        self.display_type = display_type

    def __str__(self):
        return_string = ""
        for i in self.cards:
            return_string = return_string + str(i) + "\n"
        return_string = return_string + str(self.display_type)
        return return_string

    def shuffle(self):
        random.shuffle(self.cards)

    def add(self, card_list):
        for i in card_list:
            self.cards.append(i)

    def deal(self, number_of_cards, position = 0):
        """Deletes the number of cards out of the pile, starting from
        position (default is the top) and returns that list of cards, for
        communication with other piles' .add methods."""

        dealt_list = []
        try:
            for i in range(number_of_cards):
                    dealt_list.append(self.cards[position])
                    del self.cards[position]

            return(dealt_list)
        except IndexError:
            print("Error, out of cards!")

            return(None)

I had been testing it with single objects favorably, but when I
instantiate two Pile objects, methods like .add or .shuffle affect all
of the Pile objects in memory. At first I thought the objects were all
initializing to the same space in memory, but it wasn't true. If you
need to see all my modules or my tester code, I will happily post.

Thanks for helping a rank beginner!

-Brian