Why does x,y = zip(*zip(a,b)) work in Python?

OK I love Python's zip() function. Use it all the time, it's brilliant. Every now and again I want to do the opposite of zip(), think "I used to know how to do that", then google python unzip, then remember that one uses this magical * to unzip a zipped list of tuples. Like this:

x = [1,2,3]
y = [4,5,6]
zipped = zip(x,y)
unzipped_x, unzipped_y = zip(*zipped)
unzipped_x
    Out[30]: (1, 2, 3)
unzipped_y
    Out[31]: (4, 5, 6)

What on earth is going on? What is that magical asterisk doing? Where else can it be applied and what other amazing awesome things in Python are so mysterious and hard to google?

Solution 1:

The asterisk in Python is documented in the Python tutorial, under Unpacking Argument Lists.

Solution 2:

The asterisk performs apply (as it's known in Lisp and Scheme). Basically, it takes your list, and calls the function with that list's contents as arguments.