Python Programming On Win32

Chapter 7. Building a GUI with COM

In the last chapter we built a number of Python classes that let us do some useful work in the financial domain, assuming we were happy to work at a command prompt and write our own scripts. Now we’ll embed this in a traditional GUI by exposing the Python classes as COM servers that provide an engine.

You can imagine a whole family of applications based on our classes, each specialized for a specific task such as viewing and editing data, comparing BookSets, generating forecasts and laying out reports. What you need first is a browser for your sets of accounts that can show the same types of views as the command-line version: lists of accounts, details of any account, and a date-ordered “journal.” It should also allow you to edit existing transactions and add new ones.

Our example browser is written in Visual Basic (VB) 6. We cover only a small selection of the features and code, but the full application is available with the code examples at http://starship.python.net/crew/mhammond/ppw32/. We have also built a cut-down version of the browser in Delphi; a small section at the end of the chapter explains the differences when using Delphi as a client language. Most mainstream development environments support COM, so you should be able to easily adapt what follows to your favorite development environment.