I’m a big fan of using pdb, the Python interactive debugger in conjunction with Pytest as I’m writing code.¹ With the --pdb flag, you can have Pytest drop into pdb when a test fails. With pytest.set_trace(), you can selectively enter pdb while running your tests. (I use this where I might’ve just added print statements in the past.)

A colleague uses IPython for most of his interactive development and asked me for help with some of the friction in his workflow. I recommended pdb, but he wanted to stick with the familiar IPython repl for much of his work.² He figured how to drop into an IPython repl from pdb with from IPython import embed; embed(). You can’t move up and down the call stack until you exit the repl, but you have access to all the local state you have in pdb.²

To simplify this, I recommended leveraging two little-known pdb features: alias and .pdbrc. alias allows you to set alias for statements in pdb; in this case ipy as an alias that drops into IPython:

alias ipy from IPython import embed; embed()

pdb also as the ability to load a config file from the user’s home directory or the current working directory. Each line in the file is just a pdb statement. Thus, if you can create ~/.pdbrc and add the alias statement above, the ipy command becomes available in every pdb session for your user.