Request Body Basics

Learn essential concepts of body basics in FastAPI.

What You'll Learn

This section covers request bodies, including:

• Pydantic models for request validation

• Multiple request bodies

• File uploads and form data

• Nested data structures

• Field validation and examples

• Complex request patterns

Core Concepts

Request bodies define incoming data structure:

• **Pydantic Models**: Type-safe data validation

• **Automatic Validation**: FastAPI validates automatically

• **Error Handling**: Returns 422 for invalid data

• **Documentation**: Swagger shows request schema

• **Multiple Types**: JSON, form data, files

Basic Request Body Example

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float
    description: str = None

@app.post("/items/")
async def create_item(item: Item):
    return {"id": 1, **item.dict()}

Common Request Patterns

• **JSON**: `@app.post("/items/")` with Pydantic model

• **Form Data**: `Form()` for HTML form submissions

• **File Uploads**: `UploadFile` for file handling

• **Multiple Bodies**: Combine path params + body + query

🔑 Key Takeaways

• ✅ Understand the purpose of body basics

• ✅ Know when to apply this pattern

• ✅ Follow best practices consistently

• ✅ Test thoroughly in production scenarios

Next step: Explore the advanced section for production patterns and optimization techniques.