I stumbled around a curious behaviour for tuple unpacking, which i could not explain at first. Now while typing this as a SO question it became clear, but i felt it was of enough general interest to post it nevertheless.
def test(rng):
a, b, c = rng if len(rng) == 3 else rng[0], rng[1], 1
return a, b, c
>>> test((1, 2, 3))
((1,2,3), 2, 3)
# expected: (1, 2, 3)
>>> test((1,2))
(1,2,1)
Why does it behave so unexpected at first, but makes sense at second glance?
Just add some parentheses:
>>> def test(rng):
... a, b, c = rng if len(rng) == 3 else (rng[0], rng[1], 1)
... return a, b, c
...
>>> test((1, 2, 3))
(1, 2, 3)
>>> test((1,2))
(1, 2, 1)
Currently your line is like:
a, b, c = (rng if len(rng) == 3 else rng[0]), rng[1], 1