Python array for loop

Question

Came across this for loop in a python challenge. I'm still trying to understand exactly what it's doing. Any help?

arr = [(5,8,0), (2,4)]
sum = []
for x, *y in arr:
sum = sum + y
print(sum)

https://code.sololearn.com/cP570hyz249g/?ref=app

Answer 1

A for loop runs over the primary elements of a container.

So if you wrote:

for x in arr:

x would be first a tuple of three, then a tuple of two, since that are the primary elements.

x, *y now 'unpacks' that primary element, so that you can use the parts in every iteration as x and y.

x will be the first element, and * in this context means: 'Stuff all the rest into a list named y!'

So in first iteration you can use 5 and [8, 0] with x and y, in second iteration 2 and [4].

And since you can add up lists, you get a new list with everything but the first elements.

Answer 2

Know it's late but thank you!!!