zip() and '*' before variable - what do they do?

Question

Hi, there's a Python code:

*x,y = [1,2], [3,4], [5,6],
print(list(zip(*x + [y]))[1][1])

Can someone explain me please usage of '*' before x variable and zip() function? It's really confusing.

Answer 1

'*' is a so-called greedy operator. It means it takes as much as it is allowed. In your sample *x,y = [1,2], [3,4], [5,6], the 'y' variable is the last, so it takes the last value from the values' set ([5, 6]), then "greedy" *x takes all the rest ([1,2], [3,4]).
>>> *x, y = 1,2,3,4
>>> x
[1, 2, 3]
>>> y
4
>>> x, *y = 1,2,3,4
>>> x
1
>>> y
[2, 3, 4]
>>>
>>> x, *y, z = 1,2,3,4
>>> x
1
>>> y
[2, 3]
>>> z
4
>>>
and so on.

zip in general takes several sequences as an input and returnes a special tuple where first element is firstl emelents of the input sequences:
>>> s = 'abc'
>>> t = (10, 20, 30)
>>> u = (-5, -10, -15)
>>> list(zip(s,t,u))
[('a', 10, -5), ('b', 20, -10), ('c', 30, -15)]
>>>
Note the list method called to represent zip tuple in a proper way.

Answer 2

strawdog man, that's the best explanation I've ever received! Really simple to understand, thank you!