CS 151 Project 3

Project 3: Scenes within Scenes

Main course Moodle page

The goal of this project is to incorporate loops and conditionals into your code as well as provide more practice in encapsulating code and concepts for later re-use and manipulation.


  1. Create a new file called better_shape_lib.py. Copy the goto and block functions from your Proj2/shape_lib.py file into better_shape_lib.py. Add a parameter called fill to the block function.

    First, re-write the block function to take advantage of looping, if you have not already done so.

    Second, edit the block function so that if the fill variable has the value True, then the block should be filled. If the fill variable has the value False, then the block should not be filled. You can use an if-statement before and after the drawing commands for your block to control whether to call the turtle's fill function.

    You may also want to add an optional color argument to your block function. You can specify colors for the turtle using one of two methods: as a string, or as an rgb-tuple.

    The strings you can use to specify colors are given here.

    An rgb-tuple is simply three values in the range [0.0, 1.0] as a comma-separated list surrounded by parentheses. For example:

    (0.15, 0.6, 0.2)

    makes a nice artificial grass green. You can use an rgb-tuple or a string when calling the turtle.color function. The following two calls create identical colors.

    turtle.color("Forest Green")
    turtle.color( (0.13, 0.55, 0.13) )

    Don't forget to appropriately comment your functions. In each function's doc string, state what shape it draws, and where and how big it will be (e.g. if the scale is 1, then this function will draw a house with its upper left corner at (x,y) and will be 200 pixels high and 150 pixels ide).

  2. For at least 2 more of your basic shape functions from Proj 2, copy them to your better_shape_lib.py file, edit them to use loops wherever it makes sense and give them a fill parameter that controls whether the shape is filled or not. As with the block function, you may also want to add a color argument.
  3. For at least 2 of your aggregate shapes from Proj 2, copy them to your better_shape_lib.py file, rewrite them using the new functions with the fill parameter and take advantage of looping wherever possible. The goal is to make your code as efficient as possible.

    If you wish, use conditional statements to enable variations on the complex shapes. For example, you can make any function call dependent upon a random number using the following type of test. In the example below, the block will be drawn 70% of the time.

        if random.random() < 0.7:
            block( x, y, w, h, True )
  4. Pick one of your scenes from Proj 2 (or create a brand new scene, if you wish). Copy it to your better_shape_lib.py file and re-write it so the entire scene is parameterized by an x, y location and a scale parameter. In other words, you should be able to have your scene draw anywhere on the screen at any size.

    If you have a scene that looks like the following:

    def myscene():
      block(5, 10, 50, 100)
      triangle( 5, 100, 50 )
      goto( 30, 30 )
      turtle.forward( 10 )
      turtle.left( 90 ) 
      turtle.circle( 20 )

    You can easily convert it to a scalable, moveable scene using the following rules. First, change the function to have parameters x, y, and scale.

    • For calls to a function that takes (x, y, size) or (x, y, width, height):

      block( a, b, c, d ) becomes block( x+a*scale, y+b*scale, c*scale, d*scale )

    • For calls to a goto function:

      goto( a, b ) becomes goto( x + a*scale, y + b*scale )

    • For calls to the turtle forward or circle functions:

      turtle.forward( a ) becomes turtle.forward( a * scale )

    Angles do not change. Following the above rules, the myscene function would be the following.

    def myscene(x, y, scale):
      block(x + 5*scale, y + 10*scale, 50*scale, 100*scale)
      triangle( x + 5*scale, y + 100*scale, 50*scale )
      goto( x + 30*scale, y + 30*scale )
      turtle.forward( 10*scale )
      turtle.left( 90 ) 
      turtle.circle( 20*scale )
  5. Create a taskI.py file that imports better_shape_lib.py and uses the scene function to draw several versions of the scene.

    The first required picture is an image with three differently sized versions of your arboretum scene.

  6. Create a taskII.py file that creates a museum scene. The new scene should incorporate your woodland scene at least once. For example, you could make your woodland scene appear as a window or painting within the new scene. Make sure the new scene is created inside a function.

    The second required picture is an image with your first scene located inside a second scene.

  7. Edit one of your two scenes so that some aspect of the scene depends on a new parameter. It does not have to be fancy. Set up your program so that the value of the parameter comes from a command-line argument. Create two images showing how the command line argument affects the appearance of your scene.

    The third and fourth required images should be examples of one of your scenes drawn using two different values for the command-line parameter.


Each assignment will have a set of suggested extensions. The required tasks constitute about 85% of the assignment, and if you do only the required tasks and do them well you will earn a B+. To earn a higher grade, you need to undertake one or more extensions. The difficulty and quality of the extension or extensions will determine your final grade for the assignment. One complex extension, done well, or 2-3 simple extensions are typical.

Writeup and Hand-in

Turn in your code by putting it into your private handin directory on the Courses server. All files should be organized in a folder titled Proj3 and you should include only those files necessary to run the program. We will grade all files turned in, so please do not turn in old, non-working, versions of files.

Make a new wiki page for your assignment. Put the label cs151f14project3 in the label field on the bottom of the page. But give the page a meaningful title (e.g. Stephanie's project 3).

In general, your intended audience for your write-up is your peers not in the class. Your goal should be to be able to use it to explain to friends what you accomplished in this project and to give them a sense of how you did it. Follow the outline below.