Step-by-step debugging with IPython

Solution 1:

What about ipdb.set_trace() ? In your code :

import ipdb; ipdb.set_trace()

update: now in Python 3.7, we can write breakpoint(). It works the same, but it also obeys to the PYTHONBREAKPOINT environment variable. This feature comes from this PEP.

This allows for full inspection of your code, and you have access to commands such as c (continue), n (execute next line), s (step into the method at point) and so on.

See the ipdb repo and a list of commands. IPython is now called (edit: part of) Jupyter.

ps: note that an ipdb command takes precedence over python code. So in order to write list(foo) you'd need print(list(foo)), or !list(foo) .

Also, if you like the ipython prompt (its emacs and vim modes, history, completions,…) it's easy to get the same for your project since it's based on the python prompt toolkit.

Solution 2:

You can use IPython's %pdb magic. Just call %pdb in IPython and when an error occurs, you're automatically dropped to ipdb. While you don't have the stepping immediately, you're in ipdb afterwards.

This makes debugging individual functions easy, as you can just load a file with %load and then run a function. You could force an error with an assert at the right position.

%pdb is a line magic. Call it as %pdb on, %pdb 1, %pdb off or %pdb 0. If called without argument it works as a toggle.