Debugging support in kdev-python

There's now support for (graphically) debugging python applications from within KDevelop, like it works with C++.
The implementation relies on communicating with the default python debugger, pdb, which is shipped with python. It aims to nicely map all of pdb's features to buttons and tooltips / toolviews.

kdev-python debugger in action

Features

Key features include:

• Step through code using the well-known "next", "continue", etc. buttons; KDevelop will automatically open up the source file you're currently stepping through
• Inspect the frame stack and switch between frames (toolview on the right in the above screenshot -- just click a frame to switch there)
• Set and remove breakpoints by clicking the left editor border, even while the application is running (requires extra work in plain pdb)
• A list with all local variables which is automatically updated (left toolview)
• Possibility to add custom expressions, which are automatically re-evaluated, like seen in the screenshot below
• Query the value of any expression in your code while the debugger is paused by moving the mouse over it (the value will be shown in a tooltip)
• Inspect frame stack and variables after your application crashed (i.e. threw an uncaught exception)

Automatically evaluate custom expressions (top left)

How to use it

As always, this feature is available in the master branch of kdev-python (http://projects.kde.org/kdev-python). To use the debugger, configure a script launch for your application (Run - Configure launches, Add new, then select "Script Application" in the tree view on the left under "type"), then click the "Debug" button in the toolbar.

Example launch configuration for using the debugger

Improving that launch config dialog is next on my to-do list :)

Remaining issues

There's a few things left which are currently missing or broken:

• Debugging is only supported for python 2.x applications. I will not support python 3.x before I switch to it completely (probably this summer).
• The display of the children of a variable is not optimal, it would greatly profit from heuristics about which items are important and which ones aren't (you usually don't want to inspect the __get__ method, do you).
• There's probably a few bugs left -- please report anything you find to bugs.kde.org.
• "Run to cursor" is not well written, i.e. will stop at breakpoints
• Breakpoint conditions are not supported, neither is disabling breakpoints (you can just remove them).

Inspecing the frame stack of a crashed application

Those issues will be fixed in future releases.