Why Does this Error Occur in my Python Twenty One Card Game?

Question

Here is the error:

Traceback (most recent call last): File "C:/Users/Wattel/Desktop/21 21 21.py", line 177, in main() File "C:/Users/Wattel/Desktop/21 21 21.py", line 167, in main PPOINTS, DPOINTS, PHAND, DHAND = dLoop(PHAND, DHAND, DECK) TypeError: 'NoneType' object is not iterable

I know that it has something to do with this code, but can't figure out what the problem is exactly:

scoreHAND(DHAND) < 18 or scoreHAND(DHAND) < 21 and scoreHAND(DHAND) < scoreHAND(PHAND) or scoreHAND(DHAND) < 21

Here is the rest of my code:

##21 Card Game 
##Wattel
##2016 Spring

from random import *
import random
from random import shuffle, randint

CARDPOINTS = {'AD': 11,'AH': 11,'AC': 11,'AS': 11,
              'KD': 10,'KH': 10,'KC': 10,'KS':10,
              'QD': 10,'QH': 10,'QC': 10,'QS': 10, 
              'JD': 10,'JH': 10,'JC': 10,'JS': 10,
              '10D': 10,'10H': 10,'10C': 10,'10S': 10,
              '9D': 9,'9H': 9,'9C': 9,'9S': 9,
              '8D': 8,'8H': 8,'8C': 8,'8S': 8,
              '7D': 7,'7H': 7,'7C': 7,'7S': 7,
              '6D': 6,'6H': 6,'6C': 6,'6S': 6,
              '5D': 5,'5H': 5,'5C': 5,'5S': 5,
              '4D': 4,'4H': 4,'4C': 4,'4S': 4,
              '3D': 3,'3H': 3,'3C': 3,'3S': 3,
              '2D': 2,'2H': 2,'2C': 2,'2S': 2,}

List = ['AD','AH','AC','AS',
            'KD','KH','KC','KS',
            'QD','QH','QC','QS', 
            'JD','JH','JC','JS',
            '10D','10H','10C','10S',
            '9D','9H','9C','9S',
            '8D','8H','8C','8S',
            '7D','7H','7C','7S',
            '6D','6H','6C','6S',
            '5D','5H','5C','5S',
            '4D','4H','4C','4S',
            '3D','3H','3C','3S',
            '2D','2H','2C','2S',]

def want2play():
    Hit2Play = input(" Hit 'y' to begin your game of 21): ")
    print ("")
    return Hit2Play

def deckCheck(DECK):
    print (DECK)
    print("There are:",len(DECK),"cards in the deck.") 
    if len(DECK) < 20:
        DECK = shuffleDeck() 
        return DECK
    else:
        return DECK

def openingDeal(DECK):
    PHAND = [] 
    DHAND = [] 
    DHANDT = [] 
    PHAND, DECK  = dealOneCard(PHAND, DECK) 
    DHAND, DECK = dealOneCard(DHAND, DECK)
    DHANDT.append(DHAND[0]) 
    PHAND, DECK  = dealOneCard(PHAND, DECK)
    DHAND, DECK = dealOneCard(DHAND, DECK)
    DHANDT.append("back of card")
    PPOINTS = scoreHAND(PHAND)     
    printScores_0(PPOINTS, PHAND, DHANDT)
    return PHAND, DHAND, DHANDT, DECK

def pLoop(PHAND, DHAND, DHANDT, DECK):
    while scoreHAND(PHAND) < 21:
        hitorhold = input('Do you want to hit or hold?: ')
        if hitorhold == 'hit':
            dealOneCard(PHAND, DECK)
            printScores_0(scoreHAND(PHAND), PHAND, DHANDT)
        elif hitorhold == 'hold':
            print('Player holds')
            printScores_0(scoreHAND(PHAND), PHAND, DHANDT)
            break
    return PHAND, DHAND, DECK

def dLoop(PHAND, DHAND, DECK):
    printScores_1(scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND)

    if scoreHAND(DHAND) < 18 or scoreHAND(DHAND) < 21 or scoreHAND(DHAND) < scoreHAND(PHAND) or scoreHAND(DHAND) < 21 or scoreHAND(PHAND) < 22:
        dealOneCard(DHAND, DECK)
        printScores_1(scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND)
        return scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND
    else:
        return scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND


def checkScore(pWin, dWin, PPOINTS, DPOINTS):
    if DPOINTS > PPOINTS and DPOINTS < 22:
        dWin += 1
        print (' ')
        print ("Dealer Win")
        return pWin, dWin

    elif PPOINTS == DPOINTS and PPOINTS < 21:
        dWin += 1
        print (' ')
        print ("Dealer Win")
        return pWin, dWin

    elif PPOINTS > 21 and DPOINTS < 21:
            dWin += 1
            print(' ')
            print("Dealer Win")
            return pWin, dWin

    elif PPOINTS < 22 and DPOINTS > 21:
            pWin += 1
            print (' ')
            print ("Player Win")
            return pWin, dWin

    elif PPOINTS > 21 and DPOINTS > 21:
            print (' ')
            print ("Tie.")
            return pWin, dWin

    elif PPOINTS == 21 and DPOINTS == 21:
            print(' ')
            print("Tie.")
            return pWin, dWin

def dealOneCard(HAND,DECK):
    theCard = DECK.pop(0)
    HAND.append(theCard) 
    return HAND, DECK

def shuffleDeck():
    CardPile = len(List)
    random.shuffle(List)
    return List

def scoreHAND(HAND):
    points = addScore(HAND) 
    aceCount=0
    if points > 21:
        aceCount += HAND.count('AS')
        aceCount += HAND.count('AH')
        aceCount += HAND.count('AC')
        aceCount += HAND.count('AD')
        while points > 21 and aceCount > 0:
            points -= 10
            aceCount -= 1
        return points
    else:
        return points

def addScore(HAND):
    tempScore = 0
    for i in HAND:
        tempScore += CARDPOINTS[i]
    return tempScore 

def printScores_0(POINTS, HAND, HAND1):
    print("Player's cards: ", HAND, "Player's hand score: ", POINTS)
    print("Dealer's cards: ", HAND1)

def printScores_1(PPOINTS, DPOINTS, PHAND, DHAND):
    print("Player's cards: ", PHAND, "Player's hand score: ", PPOINTS)
    print("Dealer's cards: ", DHAND, "Dealer's hand score: ", DPOINTS)

def main():
    DECK = shuffleDeck()
    pWin = 0
    dWin = 0
    while True:
        Hit2Play = want2play()
        if Hit2Play == 'y':
            DECK = deckCheck(DECK)
            PHAND, DHAND, DHANDT, DECK = openingDeal(DECK)
            PHAND, DHAND, DECK = pLoop(PHAND, DHAND, DHANDT, DECK)
            PPOINTS, DPOINTS, PHAND, DHAND = dLoop(PHAND, DHAND, DECK)
            pWin, dWin = checkScore(pWin, dWin, PPOINTS, DPOINTS)
            print("")
            print("Player's Wins:", pWin, "Dealer's Wins:",dWin)
            print("")

        else:
            print("Player's Wins:", pWin, "Dealer's Wins:",dWin)

            break
main()

Answer 1

The only problem I see with this code is in the checkScore() function, every if statement returns the same thing, but there is no return outside of the ifs. If you missed a corner case or something then this will throw an error. I suggest moving the line

return pwin, dwin

outside the if, elif block. If this does not fix your issue then try revising the dloop function; the error you receive should only happen if the function returns None.

Answer 2

Here is the final code results! Does anyone find any problems at all?

##21 Card Game 
##Wattel
##2016 Spring

from random import *
import random
from random import shuffle, randint

CARDPOINTS = {'AD': 11,'AH': 11,'AC': 11,'AS': 11,
              'KD': 10,'KH': 10,'KC': 10,'KS':10,
              'QD': 10,'QH': 10,'QC': 10,'QS': 10, 
              'JD': 10,'JH': 10,'JC': 10,'JS': 10,
              '10D': 10,'10H': 10,'10C': 10,'10S': 10,
              '9D': 9,'9H': 9,'9C': 9,'9S': 9,
              '8D': 8,'8H': 8,'8C': 8,'8S': 8,
              '7D': 7,'7H': 7,'7C': 7,'7S': 7,
              '6D': 6,'6H': 6,'6C': 6,'6S': 6,
              '5D': 5,'5H': 5,'5C': 5,'5S': 5,
              '4D': 4,'4H': 4,'4C': 4,'4S': 4,
              '3D': 3,'3H': 3,'3C': 3,'3S': 3,
              '2D': 2,'2H': 2,'2C': 2,'2S': 2,}

def shuffleDeck():

    List = ['AD','AH','AC','AS',
            'KD','KH','KC','KS',
            'QD','QH','QC','QS', 
            'JD','JH','JC','JS',
            '10D','10H','10C','10S',
            '9D','9H','9C','9S',
            '8D','8H','8C','8S',
            '7D','7H','7C','7S',
            '6D','6H','6C','6S',
            '5D','5H','5C','5S',
            '4D','4H','4C','4S',
            '3D','3H','3C','3S',
            '2D','2H','2C','2S',]
    CardPile = len(List)
    random.shuffle(List)
    return List

def want2play():
    Hit2Play = input(" Hit 'y' to begin your game of 21): ")
    print ("")
    return Hit2Play

def deckCheck(DECK):
    print (DECK)
    print("There are:",len(DECK),"cards in the deck.") 
    if len(DECK) < 20:
        DECK = shuffleDeck() 
        return DECK
    else:
        return DECK

def openingDeal(DECK):
    PHAND = [] 
    DHAND = [] 
    DHANDT = [] 
    PHAND, DECK  = dealOneCard(PHAND, DECK) 
    DHAND, DECK = dealOneCard(DHAND, DECK)
    DHANDT.append(DHAND[0]) 
    PHAND, DECK  = dealOneCard(PHAND, DECK)
    DHAND, DECK = dealOneCard(DHAND, DECK)
    DHANDT.append("back of card")
    PPOINTS = scoreHAND(PHAND)     
    printScores_0(PPOINTS, PHAND, DHANDT)
    return PHAND, DHAND, DHANDT, DECK

def pLoop(PHAND, DHAND, DHANDT, DECK):
    while scoreHAND(PHAND) < 21:
        hitorhold = input('Do you want to hit or hold?: ')
        if hitorhold == 'hit':
            dealOneCard(PHAND, DECK)
            printScores_0(scoreHAND(PHAND), PHAND, DHANDT)
        elif hitorhold == 'hold':
            print('Player holds')
            printScores_0(scoreHAND(PHAND), PHAND, DHANDT)
            break
    return PHAND, DHAND, DECK

def dLoop(PHAND, DHAND, DECK):
    printScores_1(scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND)

    if scoreHAND(DHAND) < 21 or scoreHAND(DHAND) < 21 or scoreHAND(DHAND) < scoreHAND(PHAND) or scoreHAND(DHAND) < 21 or scoreHAND(PHAND) < 22:
        dealOneCard(DHAND, DECK)
        printScores_1(scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND)
        return scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND
    else:
        return scoreHAND(PHAND), scoreHAND(DHAND), PHAND, DHAND


def checkScore(pWin, dWin, PPOINTS, DPOINTS):
    if DPOINTS > PPOINTS and DPOINTS < 22:
        dWin += 1
        print (' ')
        print ("Dealer Win")
        return pWin, dWin

    elif PPOINTS == DPOINTS and PPOINTS < 21:
        dWin += 1
        print (' ')
        print ("Dealer Win")
        return pWin, dWin

    elif PPOINTS > 21 and DPOINTS < 21:
        dWin += 1
        print(' ')
        print("Dealer Win")
        return pWin, dWin

    elif PPOINTS < 22 and DPOINTS > 21:
        pWin += 1
        print (' ')
        print ("Player Win")
        return pWin, dWin

    elif PPOINTS > 21 and DPOINTS > 21:
        print (' ')
        print ("Tie.")
        return pWin, dWin

    else:
        PPOINTS == 21 and DPOINTS == 21
        print(' ')
        print("Tie.")
        return pWin, dWin

def dealOneCard(HAND,DECK):
    theCard = DECK.pop(0)
    HAND.append(theCard) 
    return HAND, DECK

def scoreHAND(HAND):
    points = addScore(HAND) 
    aceCount=0
    if points > 21:
        aceCount += HAND.count('AS')
        aceCount += HAND.count('AH')
        aceCount += HAND.count('AC')
        aceCount += HAND.count('AD')
        while points > 21 and aceCount > 0:
            points -= 10
            aceCount -= 1
        return points
    else:
        return points

def addScore(HAND):
    tempScore = 0
    for i in HAND:
        tempScore += CARDPOINTS[i]
    return tempScore 

def printScores_0(POINTS, HAND, HAND1):
    print("Player's cards: ", HAND, "Player's hand score: ", POINTS)
    print("Dealer's cards: ", HAND1)

def printScores_1(PPOINTS, DPOINTS, PHAND, DHAND):
    print("Player's cards: ", PHAND, "Player's hand score: ", PPOINTS)
    print("Dealer's cards: ", DHAND, "Dealer's hand score: ", DPOINTS)

def main():
    DECK = shuffleDeck()
    pWin = 0
    dWin = 0
    while True:
        Hit2Play = want2play()
        if Hit2Play == 'y':
            DECK = deckCheck(DECK)
            PHAND, DHAND, DHANDT, DECK = openingDeal(DECK)
            PHAND, DHAND, DECK = pLoop(PHAND, DHAND, DHANDT, DECK)
            PPOINTS, DPOINTS, PHAND, DHAND = dLoop(PHAND, DHAND, DECK)
            pWin, dWin = checkScore(pWin, dWin, PPOINTS, DPOINTS)
            print("")
            print("Player's Wins:", pWin, "Dealer's Wins:",dWin)
            print("")

        else:
            print("Player's Wins:", pWin, "Dealer's Wins:",dWin)

            break
main()

Answer 3

I presume in your new code you made a typo, and

    else:
        PPOINTS == 21 and DPOINTS == 21
        print(' ')
        print("Tie.")
        return pWin, dWin

should be

    elif PPOINTS == 21 and DPOINTS == 21:
        print(' ')
        print("Tie.")
        return pWin, dWin

If that's the case, I wrote a quick test-frame like so:

results = [[''] * 25 for _ in range(25)]

for dp in range(25):
    for pp in range(25):
        res = checkScore(0, 0, pp, dp)
        if res is None:
            results[dp][pp] = 'N'
        else:
            p, d = res
            results[dp][pp] = ["=+","-="][d][p]

results.reverse()    # flip bottom-to-top
print("\n".join("".join(row) for row in results))

which gives (labels added): Edit: I got the scoring backwards:

      ++++++++++++++++++++++===
      ++++++++++++++++++++++===
      ++++++++++++++++++++++===
D     ---------------------=NNN
e  20 ---------------------N---
a     --------------------NN---       +  player wins
l     -------------------NNN---       =  player ties
e     ------------------NNNN---       -  player loses
r     -----------------NNNNN---
   15 ----------------NNNNNN---
P     ---------------NNNNNNN---       N  game crashes because
o     --------------NNNNNNNN---          checkScore does not
i     -------------NNNNNNNNN---          handle this combination
n     ------------NNNNNNNNNN---          of inputs
t  10 -----------NNNNNNNNNNN---
s     ----------NNNNNNNNNNNN---
      ---------NNNNNNNNNNNNN---
      --------NNNNNNNNNNNNNN---
      -------NNNNNNNNNNNNNNN---
    5 ------NNNNNNNNNNNNNNNN---
      -----NNNNNNNNNNNNNNNNN---
      ----NNNNNNNNNNNNNNNNNN---
      ---NNNNNNNNNNNNNNNNNNN---
      --NNNNNNNNNNNNNNNNNNNN---
    0 -NNNNNNNNNNNNNNNNNNNNN---

      0    5    1    1    2
                0    5    0

           Player Points

I see an awful lot of Ns there.

---

Edit 2: The solution:

The chart above should make it easy to see the geometric areas involved; we just need to rewrite checkScore to properly handle them:

def check_score(player_wins, dealer_wins, player_pts, dealer_pts):
    if dealer_pts > 21:
        if player_pts > 21:
            # no-one wins (top right square)
            print("\nTie")
            return player_wins, dealer_wins
        else:
            # player wins (top left rectangle)
            print("\nPlayer wins")
            return player_wins + 1, dealer_wins
    else:
        if player_pts > 21:
            # player loses (bottom right rectangle)
            print("\nDealer wins")
            return player_wins, dealer_wins + 1
        elif dealer_pts >= player_pts:
            # player loses (top triangle)
            print("\nDealer wins")
            return player_wins, dealer_wins + 1
        else:
            # player wins (bottom triangle)
            print("\nPlayer wins")
            return player_wins + 1, dealer_wins

and retesting gives us

++++++++++++++++++++++===
++++++++++++++++++++++===
++++++++++++++++++++++===
-------------------------
---------------------+---
--------------------++---      Problem solved!
-------------------+++---
------------------++++---
-----------------+++++---
----------------++++++---
---------------+++++++---
--------------++++++++---
-------------+++++++++---
------------++++++++++---
-----------+++++++++++---
----------++++++++++++---
---------+++++++++++++---
--------++++++++++++++---
-------+++++++++++++++---
------++++++++++++++++---
-----+++++++++++++++++---
----++++++++++++++++++---
---+++++++++++++++++++---
--++++++++++++++++++++---
-+++++++++++++++++++++---

Answer 4

For sake of comparison I wrote an OO version. Hope you learn lots from it ;-)

from random import shuffle

LOSE, TIE, WIN = -1, 0, 1

def get_yn(prompt, error_message=None, yes_values={'y','yes',''}, no_values={'n','no'}):
    """
    Prompt for input until a yes_value or no_value is entered.
    Return True for a yes_value or False for a no_value
    """
    while True:
        response = input(prompt).strip().lower()
        if response in yes_values:
            return True
        elif response in no_values:
            return False
        elif error_message is not None:
            print(error_message)

class Deck:
    SUITS  = ('D', 'H', 'C', 'S')
    FACES  = ('2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K', 'A')
    POINTS = ( 2,   3,   4,   5,   6,   7,   8,   9,   10,  10,  10,  10,  11 )

    def __init__(self):
        self.reset()

    def freshen(self):
        if len(self.cards) < 20:
            self.reset()

    def reset(self):
        self.cards = list(self.CARD_VALUES)
        shuffle(self.cards)

    def deal_to(self, hand):
        card = self.cards.pop()
        hand.cards.append(card)

# Back-patch because we cannot refer to Deck class variables until Deck is fully defined
Deck.CARD_VALUES = {f+s:p for f,p in zip(Deck.FACES, Deck.POINTS) for s in Deck.SUITS}

class Hand:
    def __init__(self):
        self.cards = []

    @property
    def points(self):
        # get sum of cards values, counting aces as 11
        card_value = Deck.CARD_VALUES.__getitem__
        total = sum(card_value(card) for card in self.cards)
        if total > 21:
            # Aces can also be counted as 1;
            #   if total is too high, try to get it <= 21
            max_aces = sum(card[0] == 'A' for card in self.cards)
            use_aces = (total - 12) // 10
            total -= 10 * min(use_aces, max_aces)
        return total

    def __str__(self):
        return "{}  ({} points)".format(" ".join(self.cards), self.points)

    def dealer_first_hand(self):
        # alternate __str__ for use while dealer's second card is hidden
        return "{} ??".format(self.cards[0])

def show_hands(player, dealer, first_hand=False):
    print("Player hand: {}".format(player))
    print("Dealer hand: {}\n".format(dealer.dealer_first_hand() if first_hand else dealer))

class TwentyOne:
    def __init__(self):
        self.deck = Deck()

    @staticmethod
    def result(player_pts, dealer_pts):
        if dealer_pts > 21:
            if player_pts > 21:
                # no-one wins (top right square)
                print("\nTie")
                return TIE
            else:
                # player wins (top left rectangle)
                print("\nPlayer wins")
                return WIN
        else:
            if player_pts > 21:
                # player loses (bottom right rectangle)
                print("\nDealer wins")
                return LOSE
            elif dealer_pts >= player_pts:
                # player loses (top triangle)
                print("\nDealer wins")
                return LOSE
            else:
                # player wins (bottom triangle)
                print("\nPlayer wins")
                return WIN

    def play(self):
        self.deck.freshen()
        player = Hand()
        dealer = Hand()
        # opening deal
        self.deck.deal_to(player)
        self.deck.deal_to(dealer)
        self.deck.deal_to(player)
        self.deck.deal_to(dealer)
        # player loop
        while player.points < 21:
            show_hands(player, dealer, True)
            if get_yn("Do you want to take another card? [Y/n] "):
                self.deck.deal_to(player)
            else:
                print("Player holds\n")
                break
        # dealer loop
        show_hands(player, dealer)
        while dealer.points < 17:
            self.deck.deal_to(dealer)
            show_hands(player, dealer)
        # tally the result
        return self.result(player.points, dealer.points)

def main():
    game   = TwentyOne()
    wins   = 0
    losses = 0
    while True:
        result  = game.play()
        wins   += (result == WIN)
        losses += (result == LOSE)
        print("Player won {}, dealer won {}\n".format(wins, losses))
        if not get_yn("Play again? [Y/n] "): break

if __name__ == "__main__":
    main()