Meaning of using commas and underscores with Python assignment operator?

Question

Reading through Peter Norvig\'s Solving Every Sudoku Puzzle essay, I\'ve encountered a few Python idioms that I\'ve never seen before.

I\'m aware that a function can

Answer 1

The _ in the Python shell also refers to the value of the last operation. Hence

>>> 1
1
>>> _
1

The commas refer to tuple unpacking. What happens is that the return value is a tuple, and so it is unpacked into the variables separated by commas, in the order of the tuple's elements.