Difference between mutation, rebinding, copying value, and assignment operator

Question

#!/usr/bin/env python3.2

def f1(a, l=[]):
    l.append(a)
    return(l)

print(f1(1))
print(f1(1))
print(f1(1))

def f2(a, b=1):
    b = b + 1
    return(a+b)

prin         


        

Answer 1

Because in f2 the name b is rebound, whereas in f1 the object l is mutated.