[IGCS] For-loop with tutle

[IGCS] For-loop with tutle

Introducing Turtle graphics

• In REPL.it, start a new "Python with Turtle" project

• Name it with "for-loop-with-turtle"

• On the first two line, do:

Enter the following in your new REPL

import turtle

t = turtle.Turtle()

Run, and on the command console, try:

• t.forward(50)

• t.left(50)

• Note what are they doing? and can you guess how to go backward and rotate right?

Drawing regular shapes

• Try to draw a square

Now try to draw the square with For-loop

Multiple Choice

Now we try to draw equilateral triangle, we need to repeat 3 times the following:

t.forward(50)

t.right([X])

What is X?

• 60

• 120

• 30

• 150

120 is the exterior angle

Can you recall the formula for it?

Exterior angle of n-side polygon

ext_angle = 360 / n

Practice time, using for loops to:

• Draw a Pentagon of each side 20 unit long

• Draw a Hexagon of 20 unit long

• Draw an Octagon of 20 unit long

• Draw a Decagon of 20 unit long

Finding the pattern

In a regular polygon:

for i in range (n):

⠀t.forward(20)

⠀t.right(?)

Summary

For loop is for counting and the counter can be used as a variable

It is usually not advisable to change the counter value inside the loop