Parameter understanding of functions in python

例子 ：
def test (x, y, z):
print (x, y, z)
def test1 (x, y, z, * args):
print (x, y, z, args)
def test2 (x, y, z, ** kw):
print (x, y, z, kw)
a = [1,2,3]
y = {'x': 1, 'y': 2, 'z': 3}
test (1 , 2,3)
test (z = 1, x = 3, y = 2)
test (* a)
test (** y)