Help understanding list operatoins inside functions in python 3

[stephen.boulet at gmail.com]

I'm a bit confused why in the second case x is not [1,2,3]:

x = []

def y():
    x.append(1)

def z():
    x = [1,2,3]

y()
print(x)
z()
print(x)

Output:
[1]
[1]