Question

I’m reading a book to read and it covers this below example.

somelist = list(SPAM)
parts = somelist[0], somelist[-1], somelist[1:3]
'first={0}, last={1}, middle={2}'.format(*parts)

Everything seems clear apart from the star being used at the end of the last line. The book fails to explain the usage of this and I hate to progress on without full understanding things.

Many thanks for your help.

Answer 1

It’s argument unpacking (kinda) operator.

args = [1, 2, 3]
fun(*args)

is the same as

fun(1, 2, 3)

(for some callable fun).

There’s also star in function definition, which means “all other positional arguments”:

def fun(a, b, *args):
    print('a =', a)
    print('b =', b)
    print('args =', args)

fun(1, 2, 3, 4) # a = 1, b = 2, args = [3, 4]