Your instructor may assign one or more of the following problems. Don’t feel that you must do all the problems; for the homeworks, you are only required to do those that are explicitly assigned via Moodle.

1. Extend your circle class from the previous homework in the following ways.

   • Make a(nother) copy of your circle.py solution and modify it so that it raises an appropriate exception when bad values are supplied to the constructor or mutators.
   • Make a copy of the circles.txt file.
   • Modify your circle_driver.py program to read a filename from the user and create a list of circles based on the specifications loaded from that file. Be sure to handle any exceptions that are likely to be raised by the user input or incorrect values in the file. You do not need to render the circles using a turtle.

   With these things in place, running circle_driver.py should work properly, with graceful exception handling, and running circle_test.py should demonstrate that the circle class is implemented correctly.

2. Extend your rectangle class from the previous homework in the ways analogous to those specified for the circle class in the previous homework problem.

3. Take your submission from lab05 (spirograph.py) and add error handling, function definitions, and fix the flow of the code:
   • Add error handling code around the code that gets the user input for the two radii and pen offset, such that the code checks if the values are legal floating point numbers (negative values are OK), and re-asks for inputs if a bad value is given. It will continue to re-ask until legal values are given.
   • Add error handling code around the code that gets the user input for the pen color, such that if the user gives a bad pen color, the code handles it and asks repeatedly until a good color has been given. Note: you can figure out if a color is good by doing turt.pencolor(the_color). If the_color is illegal, an exception is raised.
   • Create a function tryAgain() that asks the user if they would like to draw another spirograph, and checks if their answer is Y, y, n, or the empty string. It repeats the question if an illegal value is given. The function returns True if the user wants to draw another spirograph, and False otherwise. (Note: no try/except block is needed for this.)
   • Rewrite the main loop of your program such that the user is not asked immediately if they want to draw a spirograph (because, of course, they do -- they ran the program!). Instead, after the first spirograph has been drawn, it then calls tryAgain() to ask if they want to draw another.
   • If you would like to start with my spirograph code instead of your own, you may. Download it here.

Checking In

Submit all appropriate files for grading, including code files, screen captures, supplemental files (e.g., image files), and text files. We will grade this exercise according to the following criteria:

• Correctness:
  • 45% - The user interface operates correctly.
  • 30% - The main class raises exceptions as required.
• Understandability:
  • 5% - Code Documentation - Separate the logical blocks of your program with useful comments and white space.
  • 5% - Header Documentation - Document the code’s basic purpose, authors and assignment number.
  • 5% - Documentation strings - Include appropriate documentation strings for any methods
• User Experience:
  • 10% - The user interface handles raised exceptions gracefully.