How does what a user sends differ from what is actually received in processing through a path function?

When processing a request in Python, for example in web frameworks like FastAPI or Flask, the function associated with a route (path) receives data sent by the user (such as URL parameters, request body). However, inside the function, this data may be transformed or enriched.

What the user sends:

• Usually, string data (text, JSON, parameters).

What the function receives:

• The framework parses and validates the data, converting it into the required types (for example, strings to numbers, JSON to dictionaries or objects).
• Sometimes, the data is additionally enriched (for example, session information, authentication details are added).

Example in FastAPI:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float

@app.post("/items/")
async def create_item(item: Item):
    # item is already an Item object with typed fields
    return {"item_name": item.name, "item_price": item.price}

Here, the user sends a JSON with fields name and price, and the function receives an Item object with already converted types, which simplifies data handling and reduces errors.