Making Decisions with If Statements

If statements let your code choose different actions depending on conditions. This helps make drawings react to values.

Basic if example 

import turtle

size = 80
t = turtle.Turtle()
if size > 50:
    t.pencolor('red')
else:
    t.pencolor('blue')
t.forward(size)

Here the pen color depends on whether size is larger than 50.

Using if inside a loop to vary appearance 

import turtle

t = turtle.Turtle()
for i in range(8):
    if i % 2 == 0:
        t.pencolor('green')
    else:
        t.pencolor('purple')
    t.forward(80)
    t.left(45)

The loop alternates colors using a simple condition i % 2 == 0, which returns True if i is even.

Combining conditions 

import turtle

size = 60
t = turtle.Turtle()
if size > 100:
    t.pensize(5)
elif size > 50:
    t.pensize(3)
else:
    t.pensize(1)
t.forward(size)

Exercise

  • Use an if statement to choose a different shape to draw based on a variable choice. (Make sure to use == to check if things are equal, not =). For help with if statements, check out Python Conditionals.