Inheritance vs Instantiation for Python classes

[mr_byte31]

I know the meaning of Instantiation and Inheritance.
I can inherit a class and use it methods and attributes.
I also can instantiate a class and still can use the same methods and attributes !!

I am just wondering why there exists two solutions for the same problem.
is there any advantage of using one over the other (memory, speed, ..)

Inheritance:

class A:        # define your class A
pass
class B:         # define your class B
pass
class C(A, B):   # subclass of A and B

Instantiation:

class Foo():
        def __init__(self,x,y):
            print (x+y)
f = Foo(3,4)