How to Draw a Circle in Turtle Graphics

In this lesson nosotros are going to learn how to draw circles with Python Turtle Graphics. We will then change the default circumvolve method then that we can centre our circles at specific (x, y) coordinates, and and so have some fun some with creating an archery target and calculation some interactivity.

Equally you may already know, Python Turtle Graphics is fantastic fashion to learn about programming and also nearly Maths. In full general at that place seems to be little integration betwixt these two subjects at school level, which is something I promise to see modify. Many of my posts on this web log are written to help further this cause. See Computer Maths Category for related posts.

Before we start, please annotation that there are many means to achieve the aforementioned goal with Python Turtle Graphics. While this can be a good thing, it can also pb to confusion. For this reason I have washed things is a certain way which I consider gives the best foundation for making full use of the potential of this module. For example:

• I create a screen object so I can command its color and title etc.
• I use functions which have an existing turtle as an argument, to help discourage the employ of global variables and provide added flexibility, and then the same office can work for multiple turtles.

Don't worry too much almost these details if they don't make full sense to you lot. The lawmaking is fairly self explanatory and in that location are comments to help.

Drawing Circles with Python

The default way to create circles in with Python Turtle Graphics is to unproblematic use the circle method, every bit in the following example.

            import turtle  # Set up screen screen = turtle.Screen() screen.title("Circle") screen.setup(450, 450) screen.bgcolor("cyan")  # Create a turtle toby = turtle.Turtle() toby.speed(0) toby.width(5) toby.hideturtle() toby.color("reddish")  # Describe a circumvolve starting at (x, y) radius = 100 toby.circle(radius)  # Make it all work properly turtle.done()                      

This is fine for many purposes, but it can be frustrating as information technology doesn't give you command of where the center of the circumvolve is. Notice how in the example above the circle is non centred at the location of the turtle (chosen toby), which came into existence at the default location of (0, 0). Using the default method, the circle is drawn from the staring point, and then the starting indicate is on the circumference.

Cartoon Circles Centred at (10, y)

The next programme demonstrates how to draw circles centred at specific (10, y) coordinates. It does this by use of a office draw_circle() which takes several arguments as described in the code.

Using this part, it is relatively like shooting fish in a barrel to describe an archery target. Come across the programme below.

            import turtle   def draw_circle(tur, x, y, radius, color="black"):     """     Draws a circle with center at (x, y), radius radius and color color.     Create your turtle elsewhere and pass it in as tur.     """     tur.color(colour)     tur.pu()     tur.goto(x, y - radius)  # -radius because the default circle method starts drawing at the border.     tur.pd()     tur.begin_fill()     tur.circumvolve(radius)     tur.end_fill()   # Set upwards screen screen = turtle.Screen() screen.title("Archery") screen.setup(450, 450) screen.bgcolor("cyan")  # Draw the target toby = turtle.Turtle() toby.speed(0) toby.width(v) toby.hideturtle()  draw_circle(toby, 0, 0, 160, "black")  # Draw a black circle at coords (0, 0) with radius 160 pixels draw_circle(toby, 0, 0, 120, "blue") draw_circle(toby, 0, 0, eighty, "red") draw_circle(toby, 0, 0, 40, "yellow")  # Make it all work properly turtle.done()                      

This program makes use of lots of features which you can use in your ain programs. You can use equally much or as little as yous like, merely experiment with the ideas. If you don't have many ideas, endeavor simply making pocket-size changes, similar irresolute the colours or sizes of the circles. Some of the colours available in Python Turtle Graphics tin be found here.

The Next Level

This department contains some more than advanced Python programming techniques, so if you are a relative beginner, you may want to get out it for afterward on.

For example it includes

• Consequence detection with Python Turtle Graphics
• Event callback functions
• Passing boosted arguments to a callback using lambda

            import turtle  CROSS_SIZE = 20   def draw_circle(tur, x, y, radius, color="black"):     """     Draws a circumvolve with middle at (x, y), radius radius and color color.     Create your turtle elsewhere and laissez passer it in as tur.     """     tur.color(color)     tur.pu()     tur.begin_fill()     tur.goto(x, y - radius)  # -radius considering the default circle method starts drawing at the border.     tur.pd()     tur.circle(radius)     tur.end_fill()   def draw_plus(tur, 10, y, length=CROSS_SIZE):     """     Draws a cantankerous centered at (x, y) with existing turtle tur and length given by CROSS_SIZE.     """     tur.penup()     tur.goto(10, y - (length / 2))     tur.pendown()     tur.goto(10, y + (length / 2))     tur.penup()     tur.goto(x - (length / 2), y)     tur.pendown()     tur.goto(10 + (length / 2), y)     print("Mouse click at", x, ",", y)  # for useful feedback about where you clicked.   screen = turtle.Screen() screen.title("Archery") screen.setup(450, 450) screen.bgcolor("cyan") screen.mind()  # Draw cross when screen is clicked cross_turtle = turtle.Turtle(visible=False) cross_turtle.color("green") cross_turtle.width(4) cross_turtle.speed(0) # The lambda here is a useful trick to enable additional arguments to be passed to the onclick callback. screen.onclick(lambda x, y, tur=cross_turtle: draw_plus(tur, x, y)) screen.onkey(lambda: cross_turtle.clear(), "space")  # Clear crosses on keypress.  # Draw the target toby = turtle.Turtle() toby.speed(0) toby.width(5) toby.hideturtle()  draw_circle(toby, 0, 0, 160, "black")  # Depict a black circle at coords (0, 0) with radius 160 pixels draw_circle(toby, 0, 0, 120, "blue") draw_circle(toby, 0, 0, fourscore, "red") draw_circle(toby, 0, 0, 40, "yellow")  # Make information technology all piece of work properly. turtle.washed()                      

At that place are lots of ingredients hither that you can use in your own projects. As before, go ahead and edit $.25 of the program or apply bits in yous own project. The program is not currently a game as such, simply I expect information technology could exist made into i. Can you recollect of how? I'chiliad thinking some kind of random positioning of the crosses or reflex-testing game. We haven't looked at timers and animation in this article, but for sure they are possible with Python Turtle Graphics. Information technology may be that an thought you lot have might become possible with a bit more noesis, so maybe make a note and come back to information technology afterwards. If yous have an idea that yous want help with, let me know in the comments and I'll see if I tin help.

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This lesson has shown y'all how to draw circles using Python Turtle Graphics and then how to better the basic functionality and add some interactive features. I hope you found it fun and interesting.

Happy computing!

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Beginner Python Lessons

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