Chapter 14 Exercises¶

1. Fix 5 errors in the code below so that it runs correctly. It will draw red and black horizontal stripes.

   from turtle import # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) max_x = width // 2 # set the max x value to half the width sue = Turtle( # create a turtle named sue sue.pensize(10) # set the pen width for y in range(5): # repeat 5 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goTo(-1 * max_x, y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

2. The code below draws three peaks, vertically. Change 1 thing to make it draw three peaks row in a row, ^^^. (Hint: You have to change something that’s in the body of the for loop)

   from turtle import * # use the turtle library from sys import * # use the system library def draw(t, max_x): for x in range(3): t.forward(100) t.right(120) t.forward(100) t.left(120) if (t.xcor() <= max_x): t.penup() t.goto(-1 * max_x, t.ycor() - 100) t.pendown() def turtle_setup(w, t): space.setup(w, w) # set the space width and height max_x = w // 2 # set the max x value to half the width t.shape('turtle') t.penup() t.goto(-1 * max_x, 100) t.pendown() t.left(60) draw(t, max_x) setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) jaz = Turtle() width = 400 turtle_setup(width, jaz)

3. Indent lines in the code below so that it runs correctly. It will stamp 4 turtles in two different colors at the corners of a square.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) max_x = width // 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.shape("turtle") sue.penup() sue.left(45) for y in range(4): # repeat 4 times if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.forward(100) sue.stamp() sue.backward(100) sue.left(90)

4. Fix the errors so the turtle stays in a straight vertical line without leaving the screen.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) height = 400 # set the desired height space.setup(height, height) # set the space width and height max_y = height // 2 # set the max y value to half the height t = Turtle() t.shape('turtle') for x in range(10): if (100 + t.ycor() > max_y): t.color("blue") t.left(180) t.backward(100) elif (t.ycor() - 100 > (-1* max_y)): t.color("red") t.left(180) t.forward(100) else t.color("green") t.forward(100)

5. Fix 5 errors in the code below so that it runs correctly. It will draw a repeating pattern from left to right until it hits the width of the window and then will move back to the left side of the window to continue the pattern.

   from turtle * # use the turtle library from sys import * # use the system library def turtle_loop(t, max_x): for x in range(10): # repeat the body 10 times t.forward100) # go forward 100 t.right(120) # turn right 120 degrees t.forward(100) # go forward 100 t.left(120 # turn left 120 degrees if (t.xcor() >= max_x): # if at right edge of space t.penup() # pick up the pen t.goto(-1 * max_x, jaz.ycor() - 100) # move left & down t.pendown() # put the pen down def turtle_procedure(w, t): space.setup(w, w) # set the space width and height max_x = w // 2 # set the max x value to half the width t.shape('turtle') # set the shape for jaz to turtle t.penup() # pick up the pen (don't draw) t.goto(-1 * max_x, 100) # go to the left side of the space t.penDown() # put the pen down to draw with t.left(60) # turn the turtle left 60 degrees turtle_loop(t, max_x) # call the other function setExecutionLimit(50000) # let this take up to 50 seconds Space = Screen() # create a turtle screen (space) width = 400 # set the desired width jaz = Turtle() # create a turtle named jaz turtle_procedure(width, jaz)

6. The code currently draws 5 horizontal lines of alternating colors. Change it so that it draws 5 vertical lines of alternating colors.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) max_x = width // 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(5): # repeat 5 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('yellow') # set the color to yellow if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(-1 * max_x, y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

7. Change the code below to use if and else. Also fix any errors. You will need to change 3 lines. The code will draw random connected lines in alternating colors of red and black.

   from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() max_x = width // 2 # get the max x value min_x = -1 * max_x max_y = height // 2 min_y = -1 * max_y jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0 # if even row jaz.color('red') # set the color to red if num % 2 == 1: # if odd row jaz.color('black') # set the color to black rand_x = random.randrange(min_x, max_x) rand_y = random.randrange(min_y, max_y) jaz.goto(rand_x,rand_y)

8. Fix the errors in the code so it alternates between printing a horizontal yellow line and a vertical black line.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) height = space.window_height() # get the height of the screen (space) width = space.window_width # get the width max_y = height // 2 # set the max y value to half the height max_x = width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for line_num in range(4): # repeat 5 times sue.penup() # pick up the pen if line_num % 2 == 0: # if even row sue.color('yellow') # set the color to yellow sue.goto(-1 * max_x, line_num * 10) sue.penup() sue.forward(height) sue.left(90) else: # if odd row sue.color('black') # set the color to black sue.goto(line_num * 10, -1 * max_y) sue.pendown() sue.forward(height) sue.left(90)

9. Fix the indention so that the code runs correctly. Two turtles will move towards each other and then turn around and move away from each other.

   from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 40): jaz.right(45) mia.right(45)

10. Change and fix the code below so that it draws random, but connected black and red lines (it should look like scribbling) only in the bottom right half of the drawing window.

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() max_x = width // 2 # get the max x value min_x = -1 * max_x max_y = height // 2 min_y = -1 * max_y jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0 # if even row jaz.color('red') # set the color to red if num % 2 == 1 # if odd row jaz.color('black') # set the color to black rand_x = random.randrange(min_x, max_x) rand_y = random.randrange(min_y, max_y) jaz.goto(rand_x, rand_y)

11. The following code stamps a circle of turtles. Change the following code to use a different color per stamp and use at least 3 colors. You can use a counter and reset the counter to 0 after it reaches the number of colors (i.e. use a for loop and change color based off divisibility of each number). Use if, elif, and else.

    from turtle import * space = Screen() jose = Turtle() jose.shape("turtle") jose.penup() for size in range(10): jose.forward(50) jose.stamp() jose.forward(-50) jose.right(36)

12. Add to the code so that num is a random number between 1 and 3 (inclusive), and change the if clauses to be if, elif, and else. The code should draw random lines with 3 different colors based off the value of num.

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() max_x = width / 2 # get the max x value min_x = -1 * max_x max_y = height / 2 min_y = -1 * max_y jaz = Turtle() # create a turtle named jaz for x in range(10): num = if num % 3 == 0: # if even row jaz.color('red') # set the color to red if num % 2 == 1: # if odd row jaz.color('black') # set the color to black if num % 1 == 2: jaz.color('blue') rand_x = random.randrange(min_x, max_x) rand_y = random.randrange(min_y, max_y) jaz.goto(rand_x, rand_y)

13. The following code stamps turtles in a spiral. Change the code below to cycle through at least 3 colors. Use if, elif, and else.

    from turtle import * space = Screen() tess = Turtle() tess.shape("turtle") tess.penup() # ask tess to pick up her pen for size in range(5, 60, 2): # start with size = 5 and grow by 2 tess.stamp() # leave an impression on the canvas tess.forward(size) # move tess along tess.right(24) # and turn her

14. The code currently makes the two turtles just draw a circle. Fix the errors on line 13 so that the turtles move towards each other and then turn around and move away from each other.

    from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() + jaz.xcor() > 40): jaz.right(45) mia.right(45)

15. The following code draws vertical stripes alternating between red and black. Change and add code below to use 5 different colors. Use y % 5 instead of y % 2 to get 5 possible values.

    from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) max_x = width // 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(10): # repeat 10 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(-1 * max_x, y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

16. Complete and add to the turtle_loop procedure so that when the turtles collide, they move away, then turn so that they move in the same direction. It should look like a mirror image divided across the vertical axis.

    from turtle import * def turtle_loop(t1, t2): for x in range(20): t1.forward(10) t2.forward(10) if (t2.xcor() - t1.xcor() < 30): def turtle_draw(t1, t2): t1.shape('turtle') t2.shape('turtle') t2.color('red') t2.penup() t2.goto(100, 0) t2.pendown() t2.right(180) turtle_loop(t1, t2) space = Screen() jaz = Turtle() mia = Turtle() turtle_draw(jaz, mia)

17. Write a function takes a number and returns a color. It will return ‘yellow’ if the number modulus 3 is 0, ‘blue’ if it is 1, and ‘green’ if it is 2.

18. Write a procedure that takes in any number as the first parameter and a turtle as another parameter. The procedure should determine if the number is even or odd. If it is even have the turtle go right. If it is odd, have it go left. The procedure should get a random value between 1 and 2 (inclusive) and assign a color based on that number.

19. Write code that draws a pattern with the turtle with at least 3 different colors used. The code must have a for loop and must have a if statement inside the for loop that changes the color.

20. Write code that uses 2 turtles and a for loop to get a range of numbers. You should change the color of the based off if the number from the for loop is even or odd. The two turtles should move towards each other but turn away and move when they are about to intersect.