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Cover image for How to draw a filled star with Python Turtle

How to draw a filled star with Python Turtle

taarimalta profile image taarimalta Updated on ・3 min read

I overdid things a little when trying to teach 6th graders how to draw a star using Python Turtle. But I thought that it was fun anyways so I'm sharing it here.

Note that this is also my first dev.to article. I appreciate any suggestion.

Start with a zig zag

A zig-zag can be simple to explain. We just have to move the cursor left then right over and over

import turtle as t

angle=150
side=100

angle_left=angle
angle_right=angle

t.forward(side)
t.right(angle_right)
t.forward(side)
t.left(angle_left)
t.forward(side)
t.right(angle_right)
t.forward(side)
t.left(angle_left)
t.forward(side)
t.right(angle_right)
t.forward(side)
t.left(angle_left)
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Here's what we get

image

As we have repeating code we want to use a loop to reduce the code

import turtle as t

angle=150
side=100
pointies = 10

angle_left=angle
angle_right=angle

for p in range(pointies):
 t.forward(side)
 t.right(angle_right)
 t.forward(side)
 t.left(angle_left)
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Above we can change the value of pointies = 10 to change the number of zig zags

Rotate the zig zag

What happens if we rotate the zig zag by a certain value

import turtle as t

angle=150
side=100
pointies = 10
ROTATION = 30

angle_left=angle
angle_right=angle

for p in range(pointies):
 t.forward(side)
 t.right(angle_right)
 t.forward(side)
 t.left(angle_left)

 t.right(ROTATION)

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All we did above was added this statement t.right(ROTATION). We also said ROTATION = 30

and here's what we get

image

But wouldn't it be nice if the ends were connected? To achieve this we just need to set rotation to ROTATION = 360/pointies. Remember that 360 degrees is a full rotation.

import turtle as t

angle=150
side=100
pointies = 10
ROTATION = 360/pointies

angle_left=angle
angle_right=angle

for p in range(pointies):
 t.forward(side)
 t.right(angle_right)
 t.forward(side)
 t.left(angle_left)
 t.right(ROTATION)
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The result:

image

Color the star

To color the star we first set the color using t.color("red","red"). We then use the begin_fill and end_fill commands to start and stop filling the area. Here's it is:

import turtle as t

t.speed(0)

angle=150
side=100
pointies = 10
ROTATION = 360/pointies

angle_left=angle
angle_right=angle

t.color("black","red")

t.begin_fill()

for p in range(pointies):


 t.forward(side)
 t.right(angle_right)
 t.forward(side)
 t.left(angle_left)
 t.right(ROTATION)

t.end_fill()
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In the code above we have also added a statement t.speed(0) to speed things up

image

We can now draw stars with any number of points of any color. Here are some examples:

image

Rotate the star

Why stop at drawing a star when we can rotate it! To do this we use a nested for-loop. This means a loop inside a loop

import turtle as t

t.speed(0)
angle=150
side=100
pointies = 5
ROTATION = 360/pointies
angle_left=angle
angle_right=angle

t.color("red","black")

for r in range(10):

 t.begin_fill()
 for p in range(pointies):

  t.forward(side)
  t.right(angle_right)
  t.forward(side)
  t.left(angle_left)
  t.right(ROTATION)

 t.end_fill()

 t.right(2)
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In the code above we added an extra loop that runs 10 times - for r in range(10):. We have also added a t.right(2) to the end of the loop to make the turtle rotate slightly everytime the inner loop completes

Check it out:

image

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