I have been programming Python for twenty years, other languages for twenty more, and yet I use print statements almost every day.

They're fast to write, but more, I can perform a run and collect a lot of print output, and then sit down and analyze the complete run.

And you can use if statements too (yes, you can use watchpoints in your debugger). This deals with the case that you loop 1000 times and only occasionally is there a wrong number.