«< Previous

Next »>

Conditionals

Conditionals allow programs to change their behavior based on whether some statement is true or false. Let’s try this out by writing a script that will give different outputs based on the weather:

weather = "sunny"

if weather == "sunny":
    print("Bring your shades")
else:
    print("I don't know what you should bring! I'm just a little program...")

In our first line, we set a variable weather to the string “sunny,” representing what the weather is like outside. The if statement checks whether the variable weather is set to “sunny.” If it is, the code in the block beneath is executed, so the text “Bring your shades” will be printed.

The else statement handles any inputs that aren’t “sunny”—the program merely prints out that it doesn’t know what you should bring. Try this script out both with the variable set to “sunny” and the variable set to some other value.

What if we want our program to handle other kinds of weather, giving different messages for each one? Other cases after the first if statement are handled with elif:

weather = "sunny"

if weather == "sunny":
    print("Bring your shades")
elif weather == "rainy":
    print("Bring your umbrella")
elif weather == "snowy":
    print("Bring your wooly muffler")
else:
    print("I don't know what you should bring! I'm just a little program...")

You can add as many elif statements as you need, meaning that conditionals in Python have one if statement, any number of elif statements, and one else statement that catches any input not covered by if or elif. Over the next sections, we’ll work on improving this little application, making it able to handle user input directly.

Challenge

Add two more elif statements to this program to make it better able to handle different kinds of weather.

«< Previous

Next »>