Merge pull request #24 from realpython/python-type-checking

Add materials for type checking article

Author: dbader

python-type-checking/README.md

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+# The Ultimate Guide to Python Type Checking
+
+Code examples from the [The Ultimate Guide to Python Type Checking](https://realpython.com/python-type-checking/) tutorial on [Real Python](https://realpython.com/).
+

python-type-checking/dogs_001.py

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+# dogs.py
+
+from datetime import date
+
+
+class Animal:
+    def __init__(self, name: str, birthday: date) -> None:
+        self.name = name
+        self.birthday = birthday
+
+    @classmethod
+    def newborn(cls, name: str) -> "Animal":
+        return cls(name, date.today())
+
+    def twin(self, name: str) -> "Animal":
+        cls = self.__class__
+        return cls(name, self.birthday)
+
+
+class Dog(Animal):
+    def bark(self) -> None:
+        print(f"{self.name} says woof!")
+
+
+fido = Dog.newborn("Fido")
+pluto = fido.twin("Pluto")
+fido.bark()
+pluto.bark()

python-type-checking/dogs_002.py

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+# dogs.py
+
+from datetime import date
+from typing import Type, TypeVar
+
+TAnimal = TypeVar("TAnimal", bound="Animal")
+
+
+class Animal:
+    def __init__(self, name: str, birthday: date) -> None:
+        self.name = name
+        self.birthday = birthday
+
+    @classmethod
+    def newborn(cls: Type[TAnimal], name: str) -> TAnimal:
+        return cls(name, date.today())
+
+    def twin(self: TAnimal, name: str) -> TAnimal:
+        cls = self.__class__
+        return cls(name, self.birthday)
+
+
+class Dog(Animal):
+    def bark(self) -> None:
+        print(f"{self.name} says woof!")
+
+
+fido = Dog.newborn("Fido")
+pluto = fido.twin("Pluto")
+fido.bark()
+pluto.bark()

python-type-checking/game_001.py

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+# game.py
+
+import random
+
+SUITS = "♠ ♡ ♢ ♣".split()
+RANKS = "2 3 4 5 6 7 8 9 10 J Q K A".split()
+
+
+def create_deck(shuffle=False):
+    """Create a new deck of 52 cards"""
+    deck = [(s, r) for r in RANKS for s in SUITS]
+    if shuffle:
+        random.shuffle(deck)
+    return deck
+
+
+def deal_hands(deck):
+    """Deal the cards in the deck into four hands"""
+    return (deck[0::4], deck[1::4], deck[2::4], deck[3::4])
+
+
+def play():
+    """Play a 4-player card game"""
+    deck = create_deck(shuffle=True)
+    names = "P1 P2 P3 P4".split()
+    hands = {n: h for n, h in zip(names, deal_hands(deck))}
+
+    for name, cards in hands.items():
+        card_str = " ".join(f"{s}{r}" for (s, r) in cards)
+        print(f"{name}: {card_str}")
+
+
+if __name__ == "__main__":
+    play()

python-type-checking/game_002.py

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+# game.py
+
+import random
+from typing import List, Tuple
+
+SUITS = "♠ ♡ ♢ ♣".split()
+RANKS = "2 3 4 5 6 7 8 9 10 J Q K A".split()
+
+Card = Tuple[str, str]
+Deck = List[Card]
+
+
+def create_deck(shuffle: bool = False) -> Deck:
+    """Create a new deck of 52 cards"""
+    deck = [(s, r) for r in RANKS for s in SUITS]
+    if shuffle:
+        random.shuffle(deck)
+    return deck
+
+
+def deal_hands(deck: Deck) -> Tuple[Deck, Deck, Deck, Deck]:
+    """Deal the cards in the deck into four hands"""
+    return (deck[0::4], deck[1::4], deck[2::4], deck[3::4])
+
+
+def choose(items):
+    """Choose and return a random item"""
+    return random.choice(items)
+
+
+def player_order(names, start=None):
+    """Rotate player order so that start goes first"""
+    if start is None:
+        start = choose(names)
+    start_idx = names.index(start)
+    return names[start_idx:] + names[:start_idx]
+
+
+def play() -> None:
+    """Play a 4-player card game"""
+    deck = create_deck(shuffle=True)
+    names = "P1 P2 P3 P4".split()
+    hands = {n: h for n, h in zip(names, deal_hands(deck))}
+    start_player = choose(names)
+    turn_order = player_order(names, start=start_player)
+
+    # Randomly play cards from each player's hand until empty
+    while hands[start_player]:
+        for name in turn_order:
+            card = choose(hands[name])
+            hands[name].remove(card)
+            print(f"{name}: {card[0] + card[1]:<3}  ", end="")
+        print()
+
+
+if __name__ == "__main__":
+    play()

python-type-checking/game_003.py

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+# game.py
+
+import random
+import sys
+
+
+class Card:
+    SUITS = "♠ ♡ ♢ ♣".split()
+    RANKS = "2 3 4 5 6 7 8 9 10 J Q K A".split()
+
+    def __init__(self, suit, rank):
+        self.suit = suit
+        self.rank = rank
+
+    def __repr__(self):
+        return f"{self.suit}{self.rank}"
+
+
+class Deck:
+    def __init__(self, cards):
+        self.cards = cards
+
+    @classmethod
+    def create(cls, shuffle=False):
+        """Create a new deck of 52 cards"""
+        cards = [Card(s, r) for r in Card.RANKS for s in Card.SUITS]
+        if shuffle:
+            random.shuffle(cards)
+        return cls(cards)
+
+    def deal(self, num_hands):
+        """Deal the cards in the deck into a number of hands"""
+        cls = self.__class__
+        return tuple(cls(self.cards[i::num_hands]) for i in range(num_hands))
+
+
+class Player:
+    def __init__(self, name, hand):
+        self.name = name
+        self.hand = hand
+
+    def play_card(self):
+        """Play a card from the player's hand"""
+        card = random.choice(self.hand.cards)
+        self.hand.cards.remove(card)
+        print(f"{self.name}: {card!r:<3}  ", end="")
+        return card
+
+
+class Game:
+    def __init__(self, *names):
+        """Set up the deck and deal cards to 4 players"""
+        deck = Deck.create(shuffle=True)
+        self.names = (list(names) + "P1 P2 P3 P4".split())[:4]
+        self.hands = {
+            n: Player(n, h) for n, h in zip(self.names, deck.deal(4))
+        }
+
+    def play(self):
+        """Play a card game"""
+        start_player = random.choice(self.names)
+        turn_order = self.player_order(start=start_player)
+
+        # Play cards from each player's hand until empty
+        while self.hands[start_player].hand.cards:
+            for name in turn_order:
+                self.hands[name].play_card()
+            print()
+
+    def player_order(self, start=None):
+        """Rotate player order so that start goes first"""
+        if start is None:
+            start = random.choice(self.names)
+        start_idx = self.names.index(start)
+        return self.names[start_idx:] + self.names[:start_idx]
+
+
+if __name__ == "__main__":
+    # Read player names from command line
+    player_names = sys.argv[1:]
+    game = Game(*player_names)
+    game.play()