import turtle
import random
import math

screen = turtle.Screen()
screen.setup(400, 400)
screen.bgcolor('skyblue')

pen = turtle.Turtle()
pen.hideturtle()
pen.speed(0)

def draw_circle(radius, color):
    pen.penup()
    pen.goto(0, -radius)
    pen.pendown()
    pen.color(color)
    pen.begin_fill()
    pen.circle(radius)
    pen.end_fill()

draw_circle(100, 'red')
draw_circle(70, 'white')
draw_circle(40, 'red')

arrow_x = random.randint(-150, 150)
arrow_y = random.randint(-150, 150)

pen.penup()
pen.goto(arrow_x, arrow_y)
pen.color('black')
pen.dot(10)

distance = math.sqrt(arrow_x**2 + arrow_y**2)
print(f'Arrow landed at ({arrow_x}, {arrow_y})')
print(f'Distance from centre: {distance}')

screen.mainloop()

_{Project 2 — Step 3 of 5}

⭐ Step 3 — How far from the centre?

➡️ Find out how far the arrow landed from the bullseye.

We need this number so we can decide what score to give the arrow. Python has a math module with a sqrt function that we’ll use to measure the distance.

The formula is: distance = √(x² + y²) (Pythagoras!).

✏️ What to type

1. At the top, add another import:

import math

2. At the bottom (before screen.mainloop()), add:

distance = math.sqrt(arrow_x**2 + arrow_y**2)
print(f'Arrow landed at ({arrow_x}, {arrow_y})')
print(f'Distance from centre: {distance}')

import turtle
import random

screen = turtle.Screen()
screen.setup(400, 400)
screen.bgcolor('skyblue')

pen = turtle.Turtle()
pen.hideturtle()
pen.speed(0)

def draw_circle(radius, color):
    pen.penup()
    pen.goto(0, -radius)
    pen.pendown()
    pen.color(color)
    pen.begin_fill()
    pen.circle(radius)
    pen.end_fill()

draw_circle(100, 'red')
draw_circle(70, 'white')
draw_circle(40, 'red')

arrow_x = random.randint(-150, 150)
arrow_y = random.randint(-150, 150)

pen.penup()
pen.goto(arrow_x, arrow_y)
pen.color('black')
pen.dot(10)

# Add: import math at the top
# Then calculate distance = math.sqrt(arrow_x**2 + arrow_y**2)
# Print where the arrow landed and the distance

screen.mainloop()

Tap ▶ Run. You should see something like:

Arrow landed at (45, -23)
Distance from centre: 50.53711507397023

🔍 Tip

** is Python’s power sign. arrow_x**2 means “arrow_x to the power of 2” (i.e. arrow_x × arrow_x). Squaring a number is the first step of measuring distance.

Next → Step 4

_{⬅ Back to Step 2}

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_{Adapted from Raspberry Pi Foundation — Target Practice under CC BY-SA 4.0.}