Python Course 2: Bracelets and Snakes

The following code draws a snake

import turtle

SIDE = 50

def triangle():
    turtle.begin_fill()
    for n in range(3):
	turtle.forward(SIDE)
	turtle.right(120)
    turtle.end_fill()

def black_triangle():
    turtle.fillcolor("black")
    triangle()

def white_triangle():
    turtle.fillcolor("white")
    triangle()

def snake():
    black_triangle()
    turtle.forward(SIDE)
    turtle.right(60)
    white_triangle()
    turtle.left(60)

snake()

Exercise

  1. Copy the code into your IDE and run it.
  2. Draw a snake 6 segments long
  3. Draw a red and green snake, 6 segments long.
  4. Draw pink and yellow snake, 6 segments long, but half the size of the previous snake.
  5. Use a for loop to simplify your code.
  6. Now draw a snake 10 segments long

Extension

Modify your code to draw a bracelet, as shown below.

Functions and Turtle Graphics

The following code is the start of a solution to the problem of  drawing a chessboard. It uses functions to help make the code  understandable

import turtle

# Declare this at the top.  Put it in capitals to show it shouldn't be changed
SIDE = 50

def square():
    turtle.begin_fill()
    for n in range(4):
	turtle.forward(SIDE)
	turtle.right(90)
    turtle.end_fill()


def black_square():
    turtle.fillcolor("black")
    square()

def white_square():
    turtle.fillcolor("white")
    square()

def move_one_square_right():
    turtle.penup()
    turtle.forward(SIDE)
    turtle.pendown()

def move_one_square_down():
    turtle.penup()
    turtle.right(90)
    turtle.forward(SIDE)
    turtle.left(90)
    turtle.pendown()

def white_black_line():
    for n in range(4):
	white_square()
	move_one_square_right()
	black_square()
	move_one_square_right()

# Speed up the turtle
turtle.speed(0)

# Draw two lines of the chessboard
white_black_line()
turtle.home()
move_one_square_down()
move_one_square_down()
white_black_line()

Exercise

  1. Copy the code into your IDE. Watch out for indents!
  2. Run the code and see what it does.
  3. Add a function to draw a black_white() line
  4. Draw a chessboard using the functions provided
  5. Can you make you code more efficient, perhaps by using a for loop?
  6. What happens if you change the value of SIDE?
  7. Draw a 10×10 chessboard

Extension

The following function draws a hexagon:

def hexagon():
  for n in range(6):
      turtle.forward(50)
      turtle.left(60)
  1. Use the function to draw a honeycomb pattern
  2. Can you make the honeycomb cover the whole screen?

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