Skip to content

Latest commit

 

History

History
130 lines (113 loc) · 3.95 KB

03turtle.md

File metadata and controls

130 lines (113 loc) · 3.95 KB

Turtle Graphics

#Setup Open your terminal by searching for it in Spotlight on the top right. We are going to make a directory for you to put all of your projects in. Type

mkdir projects

to create the directory and then

cd projects

to enter it. Now lets create and enter a folder for this project

mkdir turtle
cd turtle

Now in Brackets or your text editor of choice, open the turtle folder with File -> Open Folder. Press Cmd-Shift-H to jump to your home directory and open the turtle folder inside projects.

Now create a new file with Cmd-N and paste the following

import turtle
winston = turtle.Turtle()


turtle.done()

Now save the file with Cmd-S and call it winston.py.

When we say import turtle we're telling python to load the code that comes with the "module" called turtle. The second line creates a turtle that we can control, and the last line keeps the window open until you close it yourself.

Now we're ready to run some code! In your terminal, navigate to the turtle folder using cd and then run winston.py in Python:

python winston.py

You should see a window open with your "turtle" in the center. You can close the window to exit the program.

Turtle Commands

Every turtle (in our case winston, or whatever you named it) can listen for commands like the following:

winston.forward(100)
winston.right(90)
winston.backward(100)

Try adding this snippet in the empty space before turtle.done() and see what it does.

Winston can respond to the following commands:

  • forward or fd: takes a distance in pixels to move forward
  • backward or bk: takes a distance in pixels to move backward
  • left or lt: takes an angle in degrees to turn left
  • right or rt: takes an angle in degrees to turn right
  • write: takes a string to write to the screen
  • setposition or goto: moves the turtle to the given (x,y) coordinates
  • penup or pu: when the turtle moves, no line will be drawn behind it
  • pendown or pd: when the turtle moves, a line will be drawn behind it
  • pensize: takes the width in pixels of the pen
  • color: takes 2 colors as strings for the pen and fill color 
    winston.color('red', 'blue')
  • fill: use this before and after drawing a shape to tell Winston to fill it 
    winston.fill(True)

# now draw a triangle
winston.forward(100)
winston.right(60)
winston.forward(100)
winston.right(60)
winston.forward(100)

winston.fill(False)

You can see a full list of commands and examples here: https://docs.python.org/2/library/turtle.html#turtle-methods

Drawing Functions

Now using these commands we can draw shapes pretty easily. To draw a square, we repeat a forward and right command 4 times:

winston.forward(100)
winston.right(90)
winston.forward(100)
winston.right(90)
winston.forward(100)
winston.right(90)
winston.forward(100)
winston.right(90)

which can be simplified by using a for loop

for i in range(4):
  winston.forward(100)
  winston.right(90)

We can take this code and turn it into a function that we can reuse. The function square will provide the size of the sides and winston will draw it

def square(size):
  for i in range(4):
    winston.forward(size)
    winston.right(90)

and now if you call square with different sizes!

Now try writing the following function

def polygon(n, size):
  # n is the number of sides for this polygon
  # size is the length of the sides
  # hint: can you find a formula for the size of the angle given the number of sides?

You can also add pen width, pen color and fill color to your polygon function.

Make some art

Now let's make a picture using this function! Draw something cool and post it on #2 Remember that you can use for loops and functions to avoid copying and pasting instructions!