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

_ is like any other variable name but usually it means "I don't care about this variable".

The second question: it is "value unpacking". When a function returns a tuple, you can unpack its elements.

>>> x=("v1", "v2")
>>> a,b = x
>>> print a,b
v1 v2