Debugging is an integral part of software development and interactive computing. A widespread debugging technique consists of placing print statements in various places in the code. Who hasn't done this? It is probably the simplest solution, but it is certainly not the most efficient (it's the poor man's debugger).

IPython is perfectly adapted for debugging, and the integrated debugger is quite easy to use (actually, IPython merely offers a nice interface to the native Python debugger pdb). In particular, tab completion works in the IPython debugger. This recipe describes how to debug code with IPython.