Why Model inheritance in FastAPI? - Purpose & Use Cases

The Big Idea

Discover how one simple trick can save you hours of tedious coding and bugs!

The Scenario

Imagine you have many data models that share common fields, like user info or timestamps, and you have to copy and paste these fields into each model manually.

The Problem

Manually repeating fields leads to mistakes, inconsistent data, and makes updates a headache because you must change every model separately.

The Solution

Model inheritance lets you define shared fields once in a base model and then extend it for specific cases, keeping your code clean and consistent.

Before vs After

✗ Before

class UserBase:
    name: str
    email: str

class UserCreate:
    name: str
    email: str
    password: str

✓ After

from pydantic import BaseModel

class UserBase(BaseModel):
    name: str
    email: str

class UserCreate(UserBase):
    password: str

What It Enables

It enables easy reuse and extension of data models, making your API code simpler and less error-prone.

Real Life Example

When building a user registration and profile system, you can have a base user model and extend it for creating users, updating profiles, or showing public info without repeating fields.

Key Takeaways

Model inheritance avoids repeating shared fields.

It keeps your code DRY (Don't Repeat Yourself).

It simplifies maintenance and reduces bugs.