CS 151: Lab 2

Project 2: A Shape Collection

Main course page

The goal of this assignment is to give you practice in creating and using functions and function parameters in Python. You'll continue to create shapes using turtle graphics, just like we did in lab.

The end result of the assignment should be a representation of a scene depicting something in the Great Maine Outdoors.

Remember that you need to write the code yourself. You can discuss the assignment and ideas regarding the assignment with others in English, but not Python. If you have questions about your Python code (other than very simple syntax questions), please ask one of the lab assistants or professors. Please see the syllabus for guidelines on collaboration and attribution.


  1. Make a copy of your lab2.py file and rename it shapelib.py (for "Shape Library"). Delete the main code from the file so that only the import statements and the functions remain. You should not have any top level code in the shapelib.py file. It is meant to form a library of shape-drawing functions that other code files will be able to import and use.

    Your first task is to create a main.py file that imports your shapelib.py functions. To do this, create a file called main.py in a text editor, and at the top (after your name and a date) put the following.

    import shapelib

    In your main.py file, make a function called outdoors1. Put a single call to the outdoors1 function at the end of the file, followed by a raw_input call.

    Write some python code in your outdoors1 function that calls some of the functions from your shapelib.py file to draw a simple image (like a few blocks). Note that to call a function from your shapelib file you have to prepend shapelib. in front of the function name. For example shapelib.block( 10, 10, 20, 30 ) would be how you would call the block function.

    You can run your main.py file using:

    python main.py

    You don't need to save this image, as you'll be replacing the code in the outdoors1 function later on.

  2. In your shapelib.py file, make 2 more functions for drawing basic shapes like the block function from lab. Basic shapes should take in at least an x location, y location, and size information. For example, you could make a triangle function or a hexagon function with the size value being the length of a side, in pixels . Put a print statement at the beginning of each function and test them out by calling the functions in your main.py function.

    Each of your shapes should draw properly no matter where it is drawn on the screen, what the size parameter is, or what the orientation of the turtle happens to be when the shape function executes. Test this out for all of your functions.

    In your writeup, include a picture demonstrating that your shape functions work properly. This is required picture 1.

    When you have a picture or scene you want to save, make a screen capture of it on a mac using the key combination Command-Shift-4. The picture will automatically be saved to a file on your Desktop. You can then move and rename it to a more appropriate location. Make sure the entire scene is visible in the image.

  3. In the shapelib.py file, make 2 functions that draw objects that you might find outdoors in Maine (e.g. a spider, a rock, a shell, a fallen branch, a leaf, a pine-cone, etc.). You can pick small objects, or big things like trees. The objects should incorporate several of the simpler shapes from your library.

    When you define these aggregate shape functions, they should all take at least three parameters. The first two (x0, y0) will define the starting location for the shape and the third should define the scale of the shape. A scale factor of 1.0 should draw the shape in its natural size. Feel free to add additional parameters as you like to control other aspects of the shape. As with the basic shapes, your shapes should draw properly at any scale, location, or turtle orientation.

    For a little more detail on making aggregate shapes, see the geometric thinking page.

    In both of of your new functions, use one or more of the basic shape functions to draw the shape. For example, a pine tree might incorporate the block and triangle functions. Test out your new functions before proceeding.

    In your writeup, include a picture demonstrating that each of your aggregate shape functions work properly. That means drawing it in several locations at several scales. This is required picture 2.

  4. Now it is time to replace the code in your outdoors1 function. Using the functions you created in steps 2 and 3, make an outdoor scene from your favorite Maine location (real or idealized). In your scene, make use of the fact that your functions can draw the shapes with different sizes in different locations. You can also use the random package and for loops to make more complex scenes, such as lots of trees or plants.

    Save the image and include it in your writeup. This is required picture 3.

  5. Make a second Great Maine Outdoors scene in a function outdoors2 in your main.py file.

    Save the image and include it in your writeup. This is required picture 4.


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, which give you the opportunity to tailor the assignment to your own interests.

How well you complete the main assignment, combined with the difficulty and quality of any extension or extensions you complete 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 "Project2". Include only those files necessary to run the program. We will grade all files and only the files in the Project2 directory, so please do not turn in old, non-working, versions of your code.

Make a new wiki page for your assignment. Put the label cs151s15project2 in the label field on the bottom of the page. Give the page a meaningful title (e.g. Stephanie's project 2).

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.