See Qiita article I tried to write it.
The basic functionality was easily made into code, but I'm wondering how to design it to expand the functionality.

# code summary
class Card
class Deck
class Player:
  def deal ()
class Dealer (Player):
  def deal ()
def blackjack ():
  # initialize deck, player, dealer
  # player.deal ()
  # dealer.deal ()
  # showdown
def confirm ()
def main ():
  while True:
    blackjack ()
    confirm ()

Assuming a one-to-one player vs dealer,
initial deal->player action->dealer action->showdowncode>initial dealandshowdownare inblackjack (), and the other two are in each classdeal ()is implemented.
Also,confirm ()outside the class is called to confirm with the player whether to draw another card withplayer.deal ().

Considering the expansion of rules, the addition of players, and the use of each class for other playing card games, features specific to blackjack can be accessed fromPlayer,DealerI think it should be divided.
I'm worried about whether I should describe all processing in the function ofblackjack (), or prepare a newBlackjackclass. Is it better to divide the processing in detail?

I have heard that processing within functions should fit within 30-40 lines.
If processing is complex, I would appreciate any advice on how to choose a function, class, or other form of implementation.

# Full code
# blackjack.py
from random import shuffle

class Card:
    suits = ["H", "D", "S", "C"]
    numbers = [i for i in range (1, 14)]
    cards_converter = {** {i: i for i in range (2, 11)},

 ** {1: "A", 11: "J", 12: "Q", 13: "K"}}
    def __init __ (self, suit, number):
        self.suit = suit
        self.number = number
    def __repr __ (self):
        return f "{self.suit}-{self.cards_converter [self.number]}"

class Deck (list):def __init __ (self):
        super () .__ init __ (Card (suit, num) for suit in Card.suits for num in Card.numbers)
        shuffle (self)

class Player:
    def __init __ (self, deck: "Deck"):
        self.deck = deck
        self.hands = []
        self._initial_deal ()
    def __repr __ (self):
        return f "{self .__ class __.__ name__}: {self.score} pts/{self.hands}"
    def _initial_deal (self)->None:
        for _ in range (2):
            self.draw ()
        print (self)
    def draw (self)->int:
        card = self.deck.pop ()
        self.hands.append (card)
        return self.score
    def deal (self)->bool:
        while confirm ("Keep drawing a card?"):
            score = self.draw ()
            print (self)
            if score == 21:
                print ("<You win!>\ n")
                return False
            elif score>21:
                print ("<You lose ...>\ n")
                return False
        print_line ()
        return True
    @property
    def score (self)->int:
        # count royal cards as 10
        score = sum (min (card.number, 10) for card in self.hands)
        # exception of ace
        if score<= 11 and 1 in {card.number for card in self.hands}:
            score + = 10
        return score

class Dealer (Player):
    def _initial_deal (self)->None:
        self.draw ()
        print (self)self.draw () # hide the second hand
    def deal (self)->bool:
        while self.score<17:
            self.draw ()
        if self.score>21:
            print (self)
            print ("<You win!>\ n") # dealer loses, and player wins
            return False
        print_line ()
        return True

def blackjack ()->None:
    # initialize/initial deal
    deck = Deck ()
    player = Player (deck)
    if player.score == 21:
        print ("<You win!>\ n")
        return
    dealer = Dealer (deck)
    # showdown
    if player.deal () and dealer.deal ():
        print (player, dealer, sep = "\ n")
        if player.score == dealer.score:
            print ("<Draw>\ n")
        elif player.score>dealer.score:
            print ("<You win!>\ n")
        else:
            print ("<You lose ...>\ n")
    print_line ()

def confirm (message: str)->bool:
    return input (f "{message} [y/n]"). lower () [0] == "y"

def print_line (length: int = 55)->None:
    print ("-" * length)

def main ():
    blackjack ()
    while confirm ("Play again?"):
        print_line ()
        blackjack ()

if __name__ == "__main__":
    main ()