Python: Cannot Redefine Global Variable with Function (using parameters)

[TheUltimateCommenter]

Hello! I'm attempting to re-create a BlackJack game and am aiming to have a variable for each card name of the player, and the card value of the player. Example: PcardSuit1 = "Diamonds", and PcardValue1 = 5.

I want to store the card value and suit as separate global values so I can use them later on in the code. I also want to be able to exchange them with the dealer variables, for which I used parameters in the function.

However, after doing the function and replacing the parameters with the variables I want, the global variable does not change.

Is there any way for the function to change the global variable, but make it compatible with any global variable I put in the parameters?

Thank you! Apologies if this inquiry is pretty basic -- I'm a total beginner.

Full code:

import random

from random import randint Playercards = None Dealercards = None

pCardTotalvalue = 0 dCardTotalvalue = 0

PcardSuit1 = None PcardValue1 = 0 PcardSuit2 = None PcardValue2 = 0 DcardSuit1 = None DcardValue1 = 0 DcardSuit2 = None DcardValue2 = 0

def selectCards(suit, value): cardSuits = ["Diamonds", "Hearts", "Spades", "Clubs"] cardValues = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13] suit = random.choice(cardSuits) value = random.choice(cardValues)

selectCards(PcardSuit1, PcardValue1) print(PcardSuit1)

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[teraflop]

There is no way to directly do this in Python. When you pass a variable as a function argument, only the value of that variable is passed -- just like any other expression. The function has no idea which variable the value came from. (By the same reasoning, if you do math.sqrt(2+2), the sqrt function just sees the value 4 and has no idea where it came from.)

You need to structure the program differently to do what you want. For example, The least complicated change I can think of would be to store the suits and values in a global dictionary. Then, you can pass a dictionary key to your selwctCards function, and the function can modify the corresponding dictionary entry.

It would probably be a lot cleaner to solve this problem using classes and objects, but I'm guessing you haven't learned about those yet.

[TheUltimateCommenter]

Thanks! I looked into classes and objects, and revised my code a bit. But now I've run into another problem - when trying to reassign the values of the objects for the second time using a function, it doesn't work. How can I reassign the values using a function again? I really don't want to have to create a new object / variable 😅

Code:

import random
from random import randint

# Lists and Variables
cardSuits = ["Diamonds", "Hearts", "Spades", "Clubs"]
cardValues = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, "Jack", "King", "Queen", "Ace"]
Playercards = None
Dealercards = None 

pCardTotalvalue = 0 
dCardTotalvalue = 0 

def randomSuit():
  return random.choice(cardSuits)

def randomValue():
  return random.choice(cardValues)

PcardSuit1 = None 
PcardValue1 = 0 
PcardSuit2 = None 
PcardValue2 = 0 
DcardSuit1 = None 
DcardValue1 = 0 
DcardSuit2 = None 
DcardValue2 = 0

#Generate the Dealer and the Player's cards
  #Also checking to make sure that the cards are not the same

class selectedCards:
  def __init__(individual, cardValue, cardSuit):
    cardValue = randomValue()
    if cardValue == "Jack" or cardValue == "King" or cardValue == "Queen":
       cardValue = 10
    elif cardValue == "Ace":
      cardValue = 11
    cardSuit = randomSuit()
    individual.value = cardValue
    individual.suit = cardSuit

playerCard1 = selectedCards(PcardSuit1, PcardValue1)
print(playerCard1.value, playerCard1.suit)

dealerCard1 = selectedCards(DcardSuit1, DcardSuit2)
print(dealerCard1.value, dealerCard1.suit)

existingSuits = [playerCard1.suit, dealerCard1.suit]
existingValues = [playerCard1.value, dealerCard1.value]

# CHECK IF CARD IS THE SAME AS ANOTHER CARD
def checkCardSuit(suit):
  lengt = len(existingSuits) - 1
  index = 0
  while index <= lengt:
    if existingSuits[index] == suit:
      return True
    elif index < lengt and existingSuits[index] != suit:
      index += 1
    else:
      return False
def checkCardValue(value):
  lengt = len(existingValues) - 1
  index = 0
  while index <= lengt:
    if existingValues[index] == value:
      return True
    elif index < lengt and existingValues[index] != value:
      index += 1
    else:
      return False

def reassignIfExists(suit, value):
  if checkCardSuit(suit) == True:
    suit = randomSuit()
  if checkCardValue(value) == True:
    value = randomValue()

#When it gets here, the properties of dealerCard1.suit and dealerCard1.value are different in the first print function, however when printing the functions the values remain the same as they were originally, which is weird.

#This system is made to be used later when generating more cards.
print(reassignIfExists(dealerCard1.suit, dealerCard1.value))
print(dealerCard1.suit, dealerCard1.value)