FastAPI Serializers and Controllers Concepts

Learning objective: By the end of this lesson, students will be able to explain what serialization is and why it is important in a FastAPI application.

What is Serialization?

Serialization is the process of converting complex data (such as Python objects) into a format that can be easily stored, shared, or sent over a network.

Why we need it in our application

FastAPI applications often need to send and receive data in JSON format when communicating with clients (like web browsers or mobile apps).
However, databases store data in a different format, such as SQLAlchemy models.

To send this data over an API, we need to convert or serialize it into JSON.
Similarly, when receiving data from a client, we must convert or deserialize JSON back into Python objects.

FastAPI makes serialization easy by using Pydantic, a library that helps define and validate data.

Pydantic

Pydantic provides three important features:

1. Data Validation

   • Before saving data to the database, Pydantic checks if it matches the expected structure.
   • For example, if a user submits an email address, Pydantic ensures it is in the correct format.

2. Serialization

   • Pydantic converts Python objects (like database models) into JSON so they can be sent over an API.

3. Typing and Data Structure

   • Pydantic allows us to define clear data models and ensures that API responses have the correct data types.

Up Next: serializing our SQLAlchemy models

In the next section, we’ll:

• Review our database models created with SQLAlchemy.
• Create Pydantic schemas to serialize the data.
• Use FastAPI to return JSON responses from the database.