The Python Apprentice

Equality of value (equivalence) versus equality of identity

Let's contrast that behavior with a test for value-equality, or equivalence. We'll create two identical lists:

>>> p = [4, 7, 11]>>> q = [4, 7, 11]>>> p == qTrue>>> p is qFalse

Here we see that p and q refer to different objects, but that the objects they refer to have the same value:

Figure 4.10:  'p' and 'q' different list objects with identical values

As you would expect when testing for value-equality, an object should always be equivalent to itself:

>>> p == pTrue

Value-equality and identity are fundamentally different notions of "equality", and it's important to keep them separate ...