Game

Now it's time to build our first game - the classic Rock, Paper, Scissors.
If you haven't read the previous sections yet, start with that, we will use much of what we learned there for this.

How does it work?

We don't start with code - we start with a plan! We can plan using pen and paper, or by writing comments in a python file.
We want the computer to secretly pick rock, paper or scissors completely at random. If we let rock = 1, scissors = 2, paper = 3, we can use the random module to generate a number between 1 and 3 for this.

After that, we want to ask the user what their selection is: 1, 2 or 3. For this, we use input.
Depending on the computer's and the user's selections, the program uses if-statements to decide whether the user won, lost, or if it's a draw.

The final structure should be something like the ofllowing: 

Try to replace the comments above with proper code before reading on. Don't worry about it not being perfect.

What we have here is often called a "specification" - a complete description of what is to be done.

The computer's choice

We previously used the random module (in the modules section), and we can do the same thing here. We use randint to generate a number between 1 and 3, and use a variable named "computer" to store what the computer selected - rock, scissors, or paper.

#  Generate a random number between 1-3 and decide to computer's choice
import random
number = random.randint(1, 3)
if number == 1:
    computer = "rock"
elif number == 2:
    computer = "scissors"
else:
    computer = "paper"

Note: This program doesn't provide any result yet, but the computer variable will be used later on.

The user's choice

Here, there is not much more to do than to ask:

# Ask the user for their choice
user = input("rock, paper or scissors?")

The user's choice is stored in the variable "user".

Who won?

If both the computer and the user picked equally, the result is a tie. We express that as:

if computer == user:
    print("It's a tie")

Otherwise, there are a couple of options, for example that the computer picked "rock" and the user picked "paper", which means that the user wins. We could write that as:

if computer == "rock" and user == "paper":
    print("You won!")

All that's left now is to fill in the remaining possibilities.

A complete program

Let's put all the parts together. Study the code carefully:

# Generate a random number between 1-3 to decide the computer's choice
import random
mumber = random.randint(1, 3)
if mumber == 1:
    computer = "rock"
elif mumber == 2:
    computer = "scissors"
else:
    computer = "paper"

# Ask the users for their choice
user = input("rock, scissors eller paper?")

# Compare the choices and print out who won
if computer == user:
    print("Oavgjort")
elif computer == "rock" and user == "paper":
    print("You won!")
elif computer == "rock" and user == "scissors":
    print("The computer won!")
elif computer == "scissors" and user == "paper":
    print("The computer won!")
elif user == "rock" and computer == "paper":
    print("The computer won!")
elif user == "rock" and computer == "scissors":
    print("You won!")
elif user == "scissors" and computer == "paper":
    print("You won!")
else:
    print(“Did you entered something strange?”)

In the video tyou can see how we build thise game, and you can copy and use the complete code above.

As you notice, the game is over after we've played it one time. Wouldn't it be nice if the game restarted when we've played it, especially if it ends in a draw? We will talk about that in the next section.