« Boston Python puzzles

Python Card Tricks

One of the least-known reasons to learn Python is for performing card tricks.

For example, Alice and Bob perform the following trick:

You choose any 5 cards from a deck. (It is a normal 52-card deck and randomly shuffled.) You give the 5 cards to Alice. Alice chooses one of the 5 cards and gives it back to you. (You hide it in your pocket.) Alice then shows the remaining 4 cards to Bob. Bob tells you what card is hidden in your pocket.

How did Alice and Bob do that?

1) Write a function called deck() that returns a randomly shuffled deck of 52 cards as a list of tuples. Each tuple should have the card's number as an integer from 1 through 13 (where 11=Jack, 12=Queen, 13=King, 1=Ace) and a single-letter string for the card's suit (Clubs, Diamonds, Hearts, Spades) like this:

[ (3,'H'), (10,'S'), (13,'C'), (8,'D'), (1,'D'), (1,'S'), ... ]

2) Figure out how to perform Alice and Bob's trick, that is, create an enciphering system that uses the order of 4 cards to uniquely encode the identity of the unknown 5th card. (There is more than one way to do this.) If you are stuck coming up with a system, here's a solution.

3) Write a Bob function. The input is a list of 4 cards, and it returns the identity of the 5th card.

4) Write an Alice function. The input is 5 randomly chosen cards from a deck. It chooses one of the 5 cards to be the mystery card and returns a list of the remaining 4 cards in the order that encodes the 5th.

5) Now put it all together into a program that allows you to perform the card trick either with you playing Alice and the computer playing Bob, or vice versa.

6) Bonus question: Can you figure out how to do the same trick, but without choosing which of the 5 cards is the mystery card?


If you have a solution you'd like to share see the Solutions page for instructions.