Identity vs Equality in Python

Satellite · Operators

Identity vs Equality

Identity compares object references; equality compares values. Mixing them up causes head-scratching bugs.

See comparisonsTest singletons properly

Examples

a = [1, 2]
b = [1, 2]
c = a

a == b  # True
a is b  # False
a is c  # True

Use == when values matter; use is for singleton objects.

Singletons

• None
• True / False
• Ellipsis, NotImplemented

Check them with is:

if value is None:
    ...

Custom classes

Override __eq__ and __hash__ to control equality semantics. Identity remains object reference (id(obj)).

Next up in your learning path

Comparison operators

Understand value comparisons fully.

Companion

Control flow

Use equality inside conditionals properly.

Practice

OOP deep dive

Override equality when modeling rich objects.

Advanced