After seeing the top-voted one, perhaps I should hesitate here. But I do remember Kevin Loney's "Controlled Flight into Terrain", on what you can do wrong with

After seeing the top-voted one, perhaps I should hesitate here. But I do remember Kevin Loney's "Controlled Flight into Terrain", on what you can do wrong with databases, as very good. I saw it at a regional Oracle users group years ago. More recently I have looked at Raymond Hettinger's "Beyond PEP 8--Best Practices for Beautiful Intelligible Code", and I hope improved my Python as a result.