Strange bugs in Python program: `str() cannot be interpreted as integer

I’m converting many of my R programs to Python (a language I don’t use on a day-to-day basis).

Here my program, which simulates a simple card game:

cards = ["Ace of Clubs",
    "Ace of Diamonds",
    "Ace of Hearts",
    "Ace of Spades",
    "2 of Clubs",
    "2 of Diamonds",
    "2 of Hearts",
    "2 of Spades",
    "3 of Clubs",
    "3 of Diamonds",
    "3 of Hearts",
    "3 of Spades",
    "4 of Clubs",
    "4 of Diamonds",
    "4 of Hearts",
    "4 of Spades",
    "5 of Clubs",
    "5 of Diamonds",
    "5 of Hearts",
    "5 of Spades",
    "6 of Clubs",
    "6 of Diamonds",
    "6 of Hearts",
    "6 of Spades",
    "7 of Clubs",
    "7 of Diamonds",
    "7 of Hearts",
    "7 of Spades",
    "8 of Clubs",
    "8 of Diamonds",
    "8 of Hearts",
    "8 of Spades",
    "9 of Clubs",
    "9 of Diamonds",
    "9 of Hearts",
    "9 of Spades",
    "10 of Clubs",
    "10 of Diamonds",
    "10 of Hearts",
    "10 of Spades",
    "Jack of Clubs",
    "Jack of Diamonds",
    "Jack of Hearts",
    "Jack of Spades",
    "King of Clubs",
    "King of Diamonds",
    "King of Hearts",
    "King of Spades",
    "Queen of Clubs",
    "Queen of Diamonds",
    "Queen of Hearts",
    "Queen of Spades"]

ticket_price = 5 # price per ticket
max_num_tickets = np.random.randint(1, 1000, 1) # maximum number of tickets sold

week = 0 # initialize counter
payoff = 0 # initialize weekly winnings
jackpot = 0 # initialize progressive jackpot

while(week < 52):
    week += 1 # increment counter
    tickets = np.random.randint(max_num_tickets + 1, size = 1) # random number of tickets sold
    fill_envelopes = np.random.choice(cards, size = len(cards), replace = False) # assign cards to envelopes
    pick_ticket = np.random.randint(tickets + 1, size = 1) # select random ticket
    pick_envelope = np.random.choice(fill_envelopes, size = 1) # choose random envelope
    cards = cards[not cards in pick_envelope] # remove selected card
    payoff = tickets * ticket_price # ticket sales
    jackpot = jackpot + (0.30 * payoff) # update weekly winnings; 30% of ticket sales goes into jackpot

    print("n Week: ", week,
        "n Ticket number: ", pick_ticket,
        "n Card selected: ", pick_envelope)

    if ("Ace of Spades" in pick_envelope):
      print("n Outcome: Congratulations, you've selected the Ace of Spades! You've won the progressive jackpot! n Jackpot: $",jackpot, "n n") 
      break
    else:
      print("n Outcome: Sorry, you didn't select the Ace of Spades! Better luck next time! n Payoff: $",(0.20 * payoff)) # 20% of ticket sales goes to winning ticket holder each week  

   print("n Proceeds donated to charity: $",(0.50 * payoff), "n n") # 50% of all ticket sales goes to charity

   cards = cards # reset deck

Appearently the bug is in the fill_envelopes line.

Here’s the error returned by the interpreter:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
mtrand.pyx in numpy.random.mtrand.RandomState.choice()

TypeError: 'str' object cannot be interpreted as an integer

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
<ipython-input-79-65a112fc8498> in <module>()
 62     week += 1 # increment counter
 63     tickets = np.random.randint(max_num_tickets + 1, size = 1) # random number of tickets sold
---> 64     fill_envelopes = np.random.choice(cards, size = len(cards), replace = False) # assign cards to envelopes
 65     pick_ticket = np.random.randint(tickets + 1, size = 1) # select random ticket
 66     pick_envelope = np.random.choice(fill_envelopes, size = 1) # choose random envelope

mtrand.pyx in numpy.random.mtrand.RandomState.choice()

ValueError: a must be 1-dimensional or an integer

It seems that the interpreter is trying to treat a string object as an integer. This was found while also encountering a TypeError.

Debugging using print statements line-by-line reveals things are working as expected. Thus, i’m a bit lost as to what’s going on here.

Answer

Two quick things: You might have just copy/pasted wrong, but you have a break outside of a loop. If you want that if/else to be in the loop, make sure it is indented correctly. The other thing, which is your actual problem: you are reusing a variable you want to remain static.

Running your code the first time works just fine, but second time breaks. Why? It has to do with this line cards = cards[not cards in pick_envelope]. Here, you replace the cards list with a single card, and then never re-make it into the original list of all 52 cards. I suspect this is actually a typo and you meant for that variable to be the singular card. If this is NOT a typo, you need to re-define the cards list to be the list of 52 cards at the start of the loop. Otherwise, the second time around the loop will have cards = 'someString', and you will get the ValueError.

EDIT: For further clarification – you are getting this error on the second go around the while loop, because you change your cards list to a string that has only one card, which happens to be the card that was ‘chosen’ in the previous iteration. You need to either make sure you don’t change the original cards list, or re-define it at the start of the loop.

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Answer