Fix loop bug in deck of cards exercise (#396)

solutions/object_oriented_design/deck_of_cards/deck_of_cards.ipynb

@@ -122,7 +122,7 @@
     "\n",
     "    def score(self):\n",
     "        total_value = 0\n",
-    "        for card in card:\n",
+    "        for card in self.cards:\n",
     "            total_value += card.value\n",
     "        return total_value\n",
     "\n",
 %% Cell type:markdown id: tags:
 
 This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer).
 
 %% Cell type:markdown id: tags:
 
 # Design a deck of cards
 
 %% Cell type:markdown id: tags:
 
 ## Constraints and assumptions
 
 * Is this a generic deck of cards for games like poker and black jack?
     * Yes, design a generic deck then extend it to black jack
 * Can we assume the deck has 52 cards (2-10, Jack, Queen, King, Ace) and 4 suits?
     * Yes
 * Can we assume inputs are valid or do we have to validate them?
     * Assume they're valid
 
 %% Cell type:markdown id: tags:
 
 ## Solution
 
 %% Cell type:code id: tags:
 
 ``` python
 %%writefile deck_of_cards.py
 from abc import ABCMeta, abstractmethod
 from enum import Enum
 import sys
 
 
 class Suit(Enum):
 
     HEART = 0
     DIAMOND = 1
     CLUBS = 2
     SPADE = 3
 
 
 class Card(metaclass=ABCMeta):
 
     def __init__(self, value, suit):
         self.value = value
         self.suit = suit
         self.is_available = True
 
     @property
     @abstractmethod
     def value(self):
         pass
 
     @value.setter
     @abstractmethod
     def value(self, other):
         pass
 
 
 class BlackJackCard(Card):
 
     def __init__(self, value, suit):
         super(BlackJackCard, self).__init__(value, suit)
 
     def is_ace(self):
         return self._value == 1
 
     def is_face_card(self):
         """Jack = 11, Queen = 12, King = 13"""
         return 10 < self._value <= 13
 
     @property
     def value(self):
         if self.is_ace() == 1:
             return 1
         elif self.is_face_card():
             return 10
         else:
             return self._value
 
     @value.setter
     def value(self, new_value):
         if 1 <= new_value <= 13:
             self._value = new_value
         else:
             raise ValueError('Invalid card value: {}'.format(new_value))
 
 
 class Hand(object):
 
     def __init__(self, cards):
         self.cards = cards
 
     def add_card(self, card):
         self.cards.append(card)
 
     def score(self):
         total_value = 0
-        for card in card:
+        for card in self.cards:
             total_value += card.value
         return total_value
 
 
 class BlackJackHand(Hand):
 
     BLACKJACK = 21
 
     def __init__(self, cards):
         super(BlackJackHand, self).__init__(cards)
 
     def score(self):
         min_over = sys.MAXSIZE
         max_under = -sys.MAXSIZE
         for score in self.possible_scores():
             if self.BLACKJACK < score < min_over:
                 min_over = score
             elif max_under < score <= self.BLACKJACK:
                 max_under = score
         return max_under if max_under != -sys.MAXSIZE else min_over
 
     def possible_scores(self):
         """Return a list of possible scores, taking Aces into account."""
         # ...
 
 
 class Deck(object):
 
     def __init__(self, cards):
         self.cards = cards
         self.deal_index = 0
 
     def remaining_cards(self):
         return len(self.cards) - deal_index
 
     def deal_card():
         try:
             card = self.cards[self.deal_index]
             card.is_available = False
             self.deal_index += 1
         except IndexError:
             return None
         return card
 
     def shuffle(self):  # ...
 ```
 
 %%%% Output: stream
 
     Overwriting deck_of_cards.py