Fall 2018", 'http://cs.colby.edu/courses/F18/cs151'); ?>

Project 2: A Shape Collection

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 related to the desert, real or imaginary. You have wide latitude in your choice of subject, and the scene can be as simple or complex as you like. What is important is to properly structure your code and include good comments.

Remember that you need to write the code yourself. You can discuss the assignment and ideas regarding the assignment with others in natural language, 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 any code not inside a function from the file so that only the import statements and the functions remain. You should not have any top level code (code not inside a function) 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, date, and description) put the following.

    import shapelib

    This lets you call any functions in your shapelib.py file, such as block, using the syntax shapelib.block. You can rename shapelib as something more concise, if you wish.

    In your main.py file, make a function called desert1. Put a single call to the desert1 function at the end of the file, followed by an input call.

    Write some python code in your desert1 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:

    python3 main.py

    You don't need to save this image, as you'll be replacing the code in the desert1 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/things that relate to the desert (e.g. cacti, lizards, snakes, flash floods, colorful rocks, natural arches, tumble weed, etc.). You can pick small objects, or big things. The objects should be built from several of the simpler shapes (triangles, blocks) 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 house shape 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 write the real code for your desert1 function. Using the functions you created in steps 2 and 3, make a scene with something related to the desert 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 stars, collections of cacti, or boulders.

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

  5. Make a second, different scene in a function desert2 in your main.py file.

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

Extension Examples

Each assignment will have a set of suggested extensions. The required tasks and writeup constitute about 83% of the assignment. If you do only the required tasks and written report -- and to 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.

These are only examples to help you start thinking of the unlimited possible ways you could extend the project. You are strongly encouraged to design your own extensions to suit your interests and show off your computational thinking skills.

Whichever extensions you choose, be sure to discuss your motivation, design process, implementation, and results in the writeup. A screenshot of your results is usually a great idea.

Hand-in and Report

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 cs151f18project2 in the label field on the bottom of the page. Give the page a meaningful title (e.g. Milo's project 2).

In general, your intended audience for your write-up is your peers not in this class, but in a similar class (such as CS152). 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.