Learning Python - Mark Lutz [53]
Beware of some IDLE usability features. IDLE does much to make life easier for beginners, but some of its tricks won’t apply outside the IDLE GUI. For instance, IDLE runs your scripts in its own interactive namespace, so variables in your code show up automatically in the IDLE interactive session—you don’t always need to run import commands to access names at the top level of files you’ve already run. This can be handy, but it can also be confusing, because outside the IDLE environment names must always be imported from files to be used.
IDLE also automatically changes both to the directory of a file just run and adds its directory to the module import search path—a handy feature that allows you to import files there without search path settings, but also something that won’t work the same when you run files outside IDLE. It’s OK to use such features, but don’t forget that they are IDLE behavior, not Python behavior.
Advanced IDLE Tools
Besides the basic edit and run functions, IDLE provides more advanced features, including a point-and-click program debugger and an object browser. The IDLE debugger is enabled via the Debug menu and the object browser via the File menu. The browser allows you to navigate through the module search path to files and objects in files; clicking on a file or object opens the corresponding source in a text edit window.
IDLE debugging is initiated by selecting the Debug→Debugger menu option in the main window and then starting your script by selecting the Run→Run Module option in the text edit window; once the debugger is enabled, you can set breakpoints in your code that stop its execution by right-clicking on lines in the text edit windows, show variable values, and so on. You can also watch program execution when debugging—the current line of code is noted as you step through your code.
For simpler debugging operations, you can also right-click with your mouse on the text of an error message to quickly jump to the line of code where the error occurred—a trick that makes it simple and fast to repair and run again. In addition, IDLE’s text editor offers a large collection of programmer-friendly tools, including automatic indentation, advanced text and file search operations, and more. Because IDLE uses intuitive GUI interactions, you should experiment with the system live to get a feel for its other tools.
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[9] IDLE is officially a corruption of IDE, but it’s really named in honor of Monty Python member Eric Idle.
[10] IDLE is a Python program that uses the standard library’s tkinter GUI toolkit (a.k.a. Tkinter in Python 2.6) to build the IDLE GUI. This makes IDLE portable, but it also means that you’ll need to have tkinter support in your Python to use IDLE. The Windows version of Python has this by default, but some Linux and Unix users may need to install the appropriate tkinter support (a yum tkinter command may suffice on some Linux distributions, but see the installation hints in Appendix A for details). Mac OS X may have everything you need preinstalled, too; look for an idle command or script on your machine.
Other IDEs
Because IDLE is free, portable, and a standard part of Python, it’s a nice first development tool to become familiar with if you want to use an IDE at all. Again, I recommend that you use IDLE for this book’s exercises if