Turtle Graphics with loops

Shapes

To start, let's try some basic designs without loops.

Square

square.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)

To add color to your design, wrap the following lines of code before and after the turtle movements.

turtle.fillcolor("green")
turtle.begin_fill()
turtle.end_fill()
import turtle
turtle.showturtle()
turtle.shape("turtle")
turtle.fillcolor("green")
turtle.begin_fill()
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)
turtle.forward(50)
turtle.right(90)
turtle.end_fill()

turtle.pencolor("red") # this statement changes the pen's color.

Rectangle

Let's draw a rectangle using variables. In Python, you name a variable and assign it a value. Replace each length and angle with a variable.

rectangle.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
length1 = 100
length2 = 200
angle = 90
turtle.forward(length1)
turtle.right(angle)
turtle.forward(length2)
turtle.right(angle)
turtle.forward(length1)
turtle.right(angle)
turtle.forward(length2)
turtle.right(angle)

Zigzag

Star

zigzag.py
import turtle
length = 25
angle = 45
turtle.showturtle()
turtle.shape("turtle")
turtle.forward(length)
turtle.right(angle)
turtle.forward(length)
turtle.left(angle)
turtle.forward(length)
turtle.right(angle)
turtle.forward(length)
turtle.left(angle)
turtle.forward(length)
turtle.right(angle)
turtle.forward(length)
turtle.left(angle)
turtle.forward(length)
turtle.right(angle)
turtle.forward(length)

Spiral

spiral.py
import turtle
length = 10
angle = 90
turtle.showturtle()
turtle.shape("turtle")
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10
turtle.forward(length+length)
turtle.right(angle)
length = length + 10

Loops

Loops are used when you have a block of code that you want to repeat.

A for loop is used when you have a block of code which you want to repeat a fixed number of times. The for loop iterates through the block of indented code.

for x in range():

x is a variable that steps through values

<do something>

do something in the indented block

for.py
for x in range(4):
    print(x)
$ python for.py
0
1
2
3
4

Square

square2.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
for x in range(4):
    turtle.forward(50)
    turtle.right(90)

Spiral

spiral2.py
import turtle
length = 10
angle = 90
turtle.showturtle()
turtle.shape("turtle")
for x in range(10):
    turtle.forward(length+length)
    turtle.right(angle)
    length = length + 10
spiral3.py
import turtle
angle = 91
turtle.showturtle()
turtle.shape("turtle")
for x in range(100):
    turtle.forward(x)
    turtle.left(angle)
circle.py
import turtle
angle = 91
turtle.showturtle()
turtle.shape("turtle")
for x in range(100):
    turtle.circle(x)
    turtle.left(angle)

Polygons

Shape

Sides

Interior Angle

Triangle

3

60

Quadrilateral

4

90

Pentagon

5

108

Hexagon

6

120

Heptagon

7

128.571

Octagon

8

135

Nonagon

9

140

Decagon

10

144

Hendecagon

11

147.273

Dodecagon

12

150

triangle.py
import turtle
length = 100
angle = 120
turtle.showturtle()
turtle.shape("turtle")
for i in range(3):
    turtle.forward(length)
    turtle.right(angle)

Star

Using a loop, we can produce an eight point star.

star1.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
turtle.pencolor('green')
for x in range(13):
        turtle.forward(200)
        turtle.left(150)

What happens if we try changing the range and the left angle?

star2.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
turtle.pencolor('purple')
for x in range(100):
        turtle.forward(200)
        turtle.left(175)

Spiral Circle

spiral.py
import turtle
turtle.showturtle()
turtle.shape("turtle")
turtle.pencolor('pink')
for i in range(180):
    turtle.forward(100)
    turtle.right(30)
    turtle.forward(20)
    turtle.left(60)
    turtle.forward(50)
    turtle.right(30)
    turtle.penup()
    turtle.setposition(0, 0)
    turtle.pendown()
    turtle.right(2)
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