How to update a counter from dictionary Python-CodePudding

I'm new to Python and coding in general and am trying to create a blackjack game in Python but I'm having trouble getting the point counter point_selection to update based on the card values in the player's hand:

deck_points = {2 : 2, 3 : 3, 4 : 4, 5 : 5, 6 : 6, 7 : 7, 8 : 8, 9 : 9, 10 : 10, 'J' : 10, 'Q' 
: 10, 'K' : 10, 'A' : 11 }

dealer_hand = []
player_hand = []

dealer_points = 0
player_points = 0

def deal_initial_cards(hand, point_selection):
    for i in range(2):
        i = random.choice(list(deck_points))
        hand.append(i)
    for card in hand:
        point_selection  = deck_points[card]

deal_initial_cards(dealer_hand, dealer_points)
print(dealer_points)

Using the above code, the counter never updates past '0' and I'm not sure what I'm doing wrong. Any help is appreciated.

CodePudding user response：

Python ints are immutable, this means dealer_points isn't updated. Initialy they have the same id(use id()), but when you change the variable inside the function it creates a new variable. To fix your code you need to do something like

deck_points = {2 : 2, 3 : 3, 4 : 4, 5 : 5, 6 : 6, 7 : 7, 8 : 8, 9 : 9, 10 : 10, 'J' : 10, 'Q' 
: 10, 'K' : 10, 'A' : 11 }

dealer_hand = []
player_hand = []

dealer_points = 0
player_points = 0

def deal_initial_cards(hand, point_selection):
    for i in range(2):
        i = random.choice(list(deck_points))
        hand.append(i)
    for card in hand:
        point_selection  = deck_points[card]
    return point_selection

dealer_points = deal_initial_cards(dealer_hand, dealer_points)
print(dealer_points)

whereas a list, which you probably noticed, is mutable. This means the list inside the function stays the same(keeps its id) even when its edited.

CodePudding user response：

Here's a more Pythonic solution that fixes your main bug about your function deal_initial_cards() operating on a copy of its (immutable) int argument point_selection then throwing away the result, since it doesn't have a return point_selection (or store the result in a class member self.points). (Also, I made all your dict keys strings: '2','3',.... It's usually customary to represent '10' as 'T' to make all cards a single letter).

But since you're essentially declaring a Hand class, then instantiating two objects of it (dealer_hand, player_hand). deal_initial_cards() is essentially a Hand._init__() in disguise, so we have a data member cards (best not to also call it hand). See how simple and clean ph = Hand() is; no need for globals. Moreover, we could statically compute points inside the __init__() function and return it (or, better, store it in self.points inside each hand object), but that would be a bad decomposition, since if we subsequently add cards to self.cards, points wouldn't get updated. So, much more Pythonic is to make points a property of the class. We then access it without parentheses: dh.points, not dh.points(). Last, note the use of a list comprehension (instead of a for-loop-append) to generate self.hand. And inside points(), note the use of a generator expression deck_points[card] for card in self.cards, again more Pythonic than for-loop counter. So this small example is a great showcase of Python idiom and decomposition. We can add a __str__() method to Hand. (You could also have a Card class, but really that would be overkill.)

import random

deck_points = {'2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9, 'T': 10, 'J' : 10, 'Q'
: 10, 'K' : 10, 'A' : 11 }

# No globals, so no need to initialize anything

class Hand:

    def __init__(self):
        self.cards = [random.choice(list(deck_points)) for _ in range(2)]

    @property
    def points(self):
        return sum(deck_points[card] for card in self.cards)

    def __str__(self, join_char=''):
        return join_char.join(card for card in self.cards)

#deal_initial_cards(dealer_hand, dealer_points)
ph = Hand()
dh = Hand()
print('Dealer: ', end='')
print(dh.points)
print('Player: ', end='')
print(ph.points)