Lesson 25: Roll a Six - Intro to Python

Roll a Six Grand finale: keep rolling a dice until you get a 6.

1import random

3def roll_dice():

4 return random.randint(1, 6)

6roll = roll_dice()

7while roll != 6:

8 print(roll)

9 roll = roll_dice()

10print("You rolled a 6!")

Terminal

$ python3 main.py

(prints a random number, different every run)

Every line, explained

import random: import loads one of Python's built-in toolboxes at the top of the file. The random toolbox is full of tools for making random numbers.
def roll_dice():: def defines a function: your own named block of code. The name is followed by round brackets and a colon, and the body is indented. Defining a function does nothing on its own: it waits until somebody calls it. In Python you must define a function before the line that calls it. Our function rolls one six-sided dice.
return random.randint(1, 6): random.randint(1, 6) hands back a random whole number from 1 to 6, both ends included. Run the program again and you will (probably) get different numbers! return hands the number back to whoever called the function; calling roll_dice() is like rolling a real dice and reading off the result.
roll = roll_dice(): Calls roll_dice and stores the number it returns. This is our first roll.
while roll != 6:: A while loop repeats its indented body for as long as the condition is True. The condition is checked again before every trip around the loop. != means "not equal": keep looping while the roll is NOT a 6.
print(roll): print(...) shows whatever is inside its round brackets in the terminal, then moves to a new line. It is written all in lowercase, and it needs both brackets. Shows each roll that wasn't a 6.
roll = roll_dice(): Rolls again, replacing the old number. Then the loop checks the condition again.
print("You rolled a 6!"): print(...) shows whatever is inside its round brackets in the terminal, then moves to a new line. It is written all in lowercase, and it needs both brackets. Outside the loop, so it runs once, the moment a 6 finally appears. You wrote a program that uses variables, a function, return, a loop and randomness. That is real programming!