Japan Flag in Python Turtle

Beginner · Flags · 38 lines · draws in about 10 seconds

This program draws the flag of Japan: a white 3:2 rectangle with a red disc in the exact centre whose diameter is 3/5 of the flag's height.

Japan Flag in Python Turtle: the finished drawing

import turtle

# The flag is 3 units wide for every 2 units high

WIDTH = 540

HEIGHT = 360

screen = turtle.Screen()

screen.title("Flag of Japan")

screen.bgcolor("#dde6ee")

t = turtle.Turtle()

t.speed(5)

# White background of the flag

t.penup()

t.goto(-WIDTH / 2, HEIGHT / 2)

t.pendown()

t.color("white")

t.begin_fill()

for side in range(2):

t.forward(WIDTH)

t.right(90)

t.forward(HEIGHT)

t.right(90)

t.end_fill()

# Red sun in the exact centre: its diameter is 3/5 of the flag's height

radius = HEIGHT * 3 / 10

t.penup()

t.goto(0, -radius)

t.pendown()

t.color("#BC002D")

t.begin_fill()

t.circle(radius, steps=90)

t.end_fill()

t.hideturtle()

turtle.done()

Open in the editor

How the code works

The white field

The pen goes to the top-left corner, then the loop draws a long side and a short side twice. The page behind is pale blue, so the white flag stands out.

# White background of the flag
t.penup()
t.goto(-WIDTH / 2, HEIGHT / 2)
t.pendown()
t.color("white")
t.begin_fill()
for side in range(2):
    t.forward(WIDTH)
    t.right(90)
    t.forward(HEIGHT)
    t.right(90)
t.end_fill()

The red disc

The disc's diameter is 3/5 of the height, so its radius is 3/10. circle() turns around a centre radius steps to the turtle's left, so starting at (0, -radius) facing east puts the centre at (0, 0), and steps=90 keeps the edge smooth.

radius = HEIGHT * 3 / 10
t.penup()
t.goto(0, -radius)
t.pendown()
t.color("#BC002D")
t.begin_fill()
t.circle(radius, steps=90)
t.end_fill()

Make it yours

Change the code above and press Run. Some ideas:

Change steps=90 to steps=8 to turn the sun into an octagon.
Change radius = HEIGHT * 3 / 10 to radius = HEIGHT * 4 / 10 and compare how much bigger the sun looks.
Change t.speed(5) to t.speed(1) and count the 90 short lines that make up the circle.

What it uses

circle with steps
begin_fill and end_fill
for loops

Every turtle command the site supports is listed on Python turtle online.