Day 10

Today

  • Classes - defining your own Python types
  • Studio work time on the text mini mini-project

For Next Time

In-Class Exercise: Geometry Classes

In this exercise, you will define methods for Line and Rect geometry classes.

Save the file geometry.py to your file system, and modify it so that the doctests pass:

python geometry.py

In order to run the doctests for a single method, comment out doctest.testmod and uncomment doctest.run_docstringexamples at the end of the file:

doctest.testmod()
# doctest.run_docstringexamples(Line.__repr_, globals())

→

# doctest.testmod()
doctest.rundocstring_examples(Line._repr_, globals())

You can use the Point class from the reading, but you are not required to.

Two of the methods in this file, Line.intersection and Rect.intersection, have their doc tests commented out. (Yes, they’re commented out within a comment.) You don’t need to implement these. They’re the subject of the third Going Beyond exercise, below.

Think about:

  1. A rectangle conceptually has left, right, top, and bottom coordinates, as well as width and height. How many of these do you need to store, and how many can be calculated? Which ones will make the implementation of the class methods simpler?
  2. Line’s initialization method takes two x coordinates in either order (x0 < x1, or x1 < x0). Is there work you could do when you initialize the object, that would make it easier to implement the methods.
  3. What are the pros and cons of adding a Square class?

[You’re encouraged to think about the first two questions before or while you perform this exercise. Think about the last question afterwards, if you have time.]_ If you have time_, you can extend your work in any of the following directions. Any of these can be done independently of the others.

Going Beyond 1: Duck Typing Skills emphasized: object-oriented programming (classes); polymorphism (“duck typing”).

Save the file geometry_beyond_1.py, implement the methods of the Circle class, and implement the function stochastic_area. stochastic_area should work on either a Rect or a Circle.

Some things to think about:

  • How close is stochastic_area’s return value to Rect and Circle’s area methods?
  • What needs to be true of a class for stochastic_area to work on it?
  • Are there additional classes that would be simple to implement, that you could apply stochastic_area to?
  • When would you use stochastic_area instead of just area?

Going Beyond 2: PyGame – Skill emphasized: computer graphics

Save the file geometry_beyond_2.py, and modify the implementation of draw_shapes to attend to its argument (a list of shapes).

Going Beyond 3: Geometry algorithms

Skill emphasized: computation geometry and computer algorithms.

You guessed it: un-comment the test cases in Line.intersection and Rect.intersection and make them pass.

Think about:

  • What should Line.intersection and Rect.intersection do when the two lines or rectangles don’t intersect? Can you think of several answers? – what are their pro and cons?

Going Beyond 4: Test Case Design

Skill emphasized: software engineering.

Think about the mistakes a non-malicious programmer could make while implementing these methods. Do the test cases detect these mistakes? What would you add?

You may do this exercise by drawing lines, squares, and points on a piece of paper, instead of covering coordinates to numbers.

Submitting Text mining-project slides

If you’d like to share what you discovered/created as part of your text mining project, please add ~1-2 slides to the class presentation [SoftDes Spring 2017 spring 2017 MP3 examples] We’ll spend time in Thursday’s class presenting your results.

Professionalism is important in public presentations, so please use the “would I be happy for my parents to read this in the newspaper” test when uploading content. Humor is great; abusive language or disparaging groups of people is firmly not acceptable.