python 3 – turtle · python 3 – turtle graphics lecture 24 – compsci111/111g ss 2016 ....
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Python 3 – Turtle graphics
Lecture 24 – COMPSCI111/111G SS 2016
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Today’s lecture u Recap
u The Turtle graphics package u Brief history u Basic commands u Drawing shapes on screen
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Logo and Turtle graphics u In 1967, Seymour Papert and Wally Feurzeig
created an interpretive programming language called Logo.
u Papert added commands to Logo so that he could control a turtle robot, which drew shaped on paper, from his computer
u Turtle graphics is now part of Python
u Using the Turtle involves instructing the turtle to move on the screen and draw lines to create the desired shape
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The Turtle package u Some functions are part of Python’s core libraries,
in other words they are ‘built-in’ u print() u input() u float()
u Other functions need to be imported into your Python program
u The turtle module needs to be imported at the start of any Python program that uses it: import turtle
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Basic Turtle commands u There are four basic turtle commands
u turtle.forward(x) u Moves turtle forward in direction it is facing by x steps
u turtle.back(x) u Moves turtle backward from its facing direction by x steps
u turtle.left(x) u Turns the turtle x degrees counterclockwise
u turtle.right(x) u Turns the turtle x degrees clockwise
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Turtle example u Using the Python interpreter in IDLE to
demonstrate how to use Turtle graphics
u First, import the turtle package
>>> import turtle >>>
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Important Information u Initial Position:
u The turtle appears as an icon
u Initial position is (0,0)
u Initial direction East (0o)
u Colour: black
u Line width: 1 pixel
u Pen: down (ready to draw)
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Exercise u Write a Python program that draws a rectangle.
The long sides must be 300 steps long and the short sides must be 150 steps long
import turtle
turtle.forward(300) turtle.left(90) turtle.forward(150) turtle.left(90) turtle.forward(300) turtle.left(90) turtle.forward(150)
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Turtle example u We can use loops when drawing shapes using
Turtle graphics
u Write a program that will draw a square using a loop
import turtle
count = 0 while count < 4: turtle.forward(200) turtle.left(90) count = count + 1
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Turtle example u We are going to draw a right-angled triangle
>>> import turtle >>> >>> turtle.forward(200) >>>
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Turtle example u Note how the turtle is now facing upward after
being turned 90 degrees left
>>> import turtle >>> >>> turtle.forward(200) >>> turtle.left(90) >>>
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Turtle example
>>> import turtle >>> >>> turtle.forward(200) >>> turtle.left(90) >>> turtle.forward(200) >>>
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Turtle example
>>> import turtle >>> >>> turtle.forward(200) >>> turtle.left(90) >>> turtle.forward(200) >>> turtle.left(135) >>>
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Turtle example u Working out the length of the longest side using
the Pythagoras’ formula
>>> import turtle >>> >>> turtle.forward(200) >>> turtle.left(90) >>> turtle.forward(200) >>> turtle.left(135) >>> c = ((200**2)+(200**2))**0.5 #around 283 steps
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Turtle example u The finished image
>>> import turtle >>> >>> turtle.forward(200) >>> turtle.left(90) >>> turtle.forward(200) >>> turtle.left(135) >>> c = ((200**2)+(200**2))**0.5) >>> turtle.forward(c)
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Turtle example u Write a program that will draw a circle
import turtle count = 0 while(count < 360): turtle.forward(2) turtle.left(1) count = count + 1 print("Finished!")
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What Shape is this? u import turtle
u count = 0
u length = 100
u while count < 4: u turtle.forward(length) u turtle.left(90) u count = count + 1 u length = length -10
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How to draw a star import turtle
count = 0
while count < 5: turtle.forward(300) turtle.left(180-36) count = count + 1
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Exercise u Draw the shape that is produced by the following
Python program: import turtle count = 0 while(count < 180): turtle.forward(2) turtle.right(1) count = count + 1
turtle.right(45) turtle.forward(300) turtle.left(90) turtle.back(150) turtle.right(45) turtle.back(250)
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Exercise import turtle big_line = 100 little_line = 50 angle = 90 turtle.left(angle) turtle.forward(big_line) count = 0 while count < 4:
turtle.right(angle//2) if count != 3: turtle.forward(little_line) else: turtle.forward(big_line) count = count + 1
turtle.right(90) turtle.forward(130)
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Summary u The Turtle package must be imported into every
Python program that uses it
u The Turtle has four basic commands; forward, back, left and right