How to implement guide with fastapi and pydantic model validation scenarios on nested structures in python 3.11
I'm working with FastAPI and using Pydantic for data validation, but I'm working with an scenario where the validation of nested models is failing unexpectedly. My API endpoint is supposed to accept a JSON object that contains an array of items, each with its own nested structures. Here's a snippet of the relevant parts: ```python from fastapi import FastAPI from pydantic import BaseModel, conlist app = FastAPI() class Item(BaseModel): name: str quantity: int class Order(BaseModel): order_id: int items: conlist(Item, min_items=1) @app.post("/orders/") async def create_order(order: Order): return order ``` When I send a request with the following JSON body: ```json { "order_id": 123, "items": [ {"name": "Item A", "quantity": 2}, {"name": "Item B", "quantity": "three"} ] } ``` I encounter a validation behavior that states: ``` ValidationError: 1 validation behavior for Order items -> 1 -> quantity value is not a valid integer (type=type_error.integer) ``` I have done some debugging and confirmed that the scenario arises specifically with the `quantity` field when it is not an integer. However, I expected Pydantic to handle this by returning an informative behavior related to the whole order structure. Is there a way to customize the behavior messages or handle them more gracefully? Also, how can I ensure that my validation for nested models provides clearer feedback on where the scenario lies without throwing a generic behavior? Iām using Python 3.11 along with FastAPI 0.95.1 and Pydantic 1.10.2. Any pointers in the right direction? This is part of a larger CLI tool I'm building. Am I approaching this the right way?