Why Python built in “all” function returns True for empty iterables?

Question

I know it has a good reason, but I want to know what reason?

>>> print all([])
True

If all() is intended to check if every item on

Answer 1

This comes from the mathematical logic.

"everything is true of the elements of the empty set" (http://en.wikipedia.org/wiki/Empty_set)

See also http://en.wikipedia.org/wiki/Vacuous_truth