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import turtle 
This line needs to be included 
at the beginning of your 
program to import the turtle 
library into Python, allowing 
you to use the turtle functions. 
scr = turtle.Screen() 
Defines the window as being 
called “scr”. This means we can 
use the shorthand “scr”, rather 
than having to refer to the window 
by its full name each time. 
scr.bgcolor(“yellow”) 
Sets the screen background 
colour to yellow. By default, the 
background colour will be 
white unless it is changed. 
turtle.pensize(3) 
Changes the turtle pen size 
(the thickness of the line that is 
drawn) to 3. By default, this is 1 
unless it is changed. 
turtle.penup() 
Removes the pen from 
the page so that as the 
turtle moves it does not 
leave a trail behind it. 
turtle.pendown() 
Places the pen on the 
page so that when the 
turtle moves it will 
leave a trail behind it. 
By default, the pen is 
down unless specified 
otherwise.