difference between forms of input a list to function

[akbarza]

hi
what is difference between f(b) and f(b[:]) in below? when i run them the outputs are different
1)

b=[1,2]
id(b)
def f(a):
    a[0]=3
    print("a: ",a, "id(a): ",id(a))

f(b)
print("b , id(b)",b,id(b))

2)

b=[1,2]
id(b)
def f(a):
    a[0]=3
    print("a: ",a, "id(a): ",id(a))
f(b[:])
print("b , id(b)",b,id(b))

please explain, thanks