Debugging Python on Emacs IDE

I've tried a few IDEs for standalone Python development. But end of the day I came back to Emacs. I love Emacs because it is lightweight, I can pretty much do whatever I can with any other IDE and much more if I write some Lisp script.

Here in this article, I'd just cover how to step through your standalone Python code and debug it using Emacs as the editor/IDE. First of all you have to install the following Emacs extension modules and Python debugging tools.

• Install Pymacs from this github site and thank François Pinard of Montreal for programming it
• Install Rope and Ropemacs from here (using Mercury)
• Check if you have PDB, just by typing it on command window (you'd mostly have)

Now the step-by-step debugging goes like this

1. With your Python program on buffer, type M-x pdb. It would ask if you want to run PDB like, pdb a.out. Replace a.out with your Python module name. In the screenshot, it is adder.py (doing nothing useful).
2. This opens a new PDB windows (Screenshot)
3. Go to the lines where you need breakpoint, type C-x (you can notice the screenshot for the statement about it). If you are using Ubuntu, you get a very good look-n-feel, like that screenshot.
4. Type c on the PDB buffer to run upto the breakpoint
5. From the breakpoint, n for next line or s to explore into functions on that line. In Ubuntu, you'd have a GUI to assist you.
6. To watch a variable, type p var, as in the screenshot.
7. Any time during debugging, w prints out the stack and u and d lets you go up and down the stack.

For most of the standalone Python script, this would improve your productivity a lot. You can do more complex debug operations, but this is a very good start.