Programming Python, 3rd Edition

PyEdit: A Text Editor Program/Object

In the last few decades, I’ve typed text into a lot of programs. Most were closed systems (I had to live with whatever decisions their designers made), and many ran on only one platform. The PyEdit program presented in this section does better on both counts: it implements a full-featured, graphical text editor program in roughly 600 lines of portable Python code (including whitespace, comments, and configuration settings). Despite its size, PyEdit was sufficiently powerful and robust to serve as the primary tool used to code most of the examples in this book.

PyEdit supports all the usual mouse and keyboard text-editing operations: cut and paste, search and replace, open and save, undo and redo, and so on. But really, PyEdit is a bit more than just another text editor—it is designed to be used as both a program and a library component, and it can be run in a variety of roles:

Standalone mode

As a standalone text-editor program, with or without the name of a file to be edited passed in on the command line. In this mode, PyEdit is roughly like other text-editing utility programs (e.g., Notepad on Windows), but it also provides advanced functions such as running Python program code being edited, changing fonts and colors, and so on. More important, because it is coded in Python, PyEdit is easy to customize, and it runs portably on Windows, X Windows, and Macintosh.

Pop-up mode

Within a new pop-up window, allowing an arbitrary number of copies to appear ...