This is an example for working with legacy code that I use in teaching.

The code is the Python version of the example that Brett Schuchert has used in talks about working with legacy code.

• Watch him work with the C# version: http://vimeo.com/34484105
  • Get the code here.
• See "A story about too much power" for a written treatment of the Java version of this example.

Git branches

• master The legacy code we start out with.
• golden_master Now we have an integration test and a pseudo-unit test that uses a Python form of monkey patching: namespace overriding.
• solution is not complete, but a significant step forward.
  • Classes extracted.
  • Class for currency symbols extracted.
  • Extracted caching to decorator pattern. – While very OO, this is not very Pythonic. What would be a better solution? Something with Python decorators?

Credits

Thanks to Brett Schuchert for this prolific example – and for generally publishing everything on his wiki under the Creative Commons Attribution-ShareAlike license.

License

This material is published under the same CC BY-SA 2.5 license as Brett’s talk.