5.2 Python Object Model

Everything Is an Object

What Is It?

In Python, literally everything — numbers, strings, functions, even classes themselves — is an object with its own identity, type, and value.

Why Does It Matter?

This uniformity is why the same tools (type(), dir(), hasattr()) work on any value, no matter what kind it is.

Every Python value is an object with three properties: identity, type, and value.

Identity

What Is It?

A unique integer identifying an object for its lifetime — effectively its memory address in CPython.

How Is It Used?

id(x) returns it; the is operator compares two objects’ identities.

>>> a = 5
>>> id(a)
11755816

Type

What kind of object it is, and therefore what operations are valid on it. Retrieved with type().

>>> type(a)
<class 'int'>

Value

The actual data the object holds — 5, "hello", [1, 2, 3]. For mutable objects the value can change over the object’s lifetime; for immutable objects it cannot (see 5.9 Mutable vs Immutable Types).

Quick Interview Answer

“Every Python object has three properties: identity (a unique id, effectively its memory address in CPython, from id()), type (what kind of object it is, from type()), and value (the actual data it holds). This uniform model is why the same tools — type(), dir(), hasattr() — work identically on any value, since everything, even a function or a class, is an object.”

Common Mistakes

• Confusing id() (identity, a memory address) with type() (what kind of object it is) — they answer completely different questions.
• Comparing objects with is when == (value equality) is what’s actually intended — is checks identity, not value.