7,291 questions
Score of 1
1 answer
111 views
How to express a conditionally required parameter in a Pydantic-validated tool/API schema, without losing the upfront schema validation?
I have a function (specifically an MCP tool built with FastMCP, but this is really a Pydantic/JSON Schema question) where one parameter is required in the normal case, but must be optional when a ...
- reputation score 83
Score of -4
1 answer
167 views
Is there a better alternative to using os.getenv() for FastAPI settings?
I'm building a FastAPI application and currently manage my environment variables using python-dotenv and os.getenv().
My current implementation is:
from dotenv import load_dotenv
import os
...
- reputation score 7
Score of 3
1 answer
135 views
How can I prevent duplicate Celery tasks when a FastAPI endpoint is retried?
I'm using FastAPI + Celery + Redis + PostgreSQL for a document-processing workflow.
A FastAPI endpoint creates a processing job and then sends a Celery task:
@app.post("/reports/{report_id}/...
- reputation score 31
Score of 0
1 answer
120 views
FastAPI Form() with List[Type] sends array as comma-separated string ("2,5") causing 422 parsing error in Swagger UI
Here's a Minimal, Reproducible Example:
from fastapi import FastAPI, Form
from typing import Annotated, List
app = FastAPI()
@app.post('/')
def create(arr: Annotated[List[int], Form()] = []):
...
- reputation score 161
Score of -5
1 answer
116 views
An error during using my FastAPI app. ValueError: [TypeError('object is not iterable'), TypeError('vars() argument must have __dict__ attribute')]
I'm trying to make my FastAPI app for using my trained ML-model, but I get this error
ValueError: [TypeError('object is not iterable'), TypeError('vars()
argument must have __dict__ attribute')]
...
- reputation score 3
Score of -3
1 answer
122 views
How to extend FastAPI's OAuth2PasswordBearer logout feature?
I'm using FastAPI for my backend and I already have /login and /logout endpoints for my frontend to talk to and I'm also using fastapi's OAuth2PasswordBearer (that points to a debug endpoint) to use ...
- reputation score 4
Score of -4
2 answers
164 views
How to solve the problem with None async engine in sqlalchemy before closing engine?
I have simple backend async application on fastapi and sqlalchemy.
Here code of my application:
main.py:
import uvicorn
import asyncio
from fastapi import FastAPI
from src.web.main_web_handler import ...
- reputation score 33
Score of 0
1 answer
183 views
FastAPI event loop blocked by Scikit-Learn Joblib thread-pool exhaustion during concurrent async inference
I am deploying a Random Forest model using FastAPI. Because Scikit-Learn models are synchronous and CPU-bound, I am offloading the inference to asyncio.get_running_loop().run_in_executor() to prevent ...
- reputation score 41
Score of 3
1 answer
243 views
FastAPI returning "Out of range float values are not JSON compliant" with Pandas NaN values
I am building a FastAPI endpoint that reads data, processes it into a Pandas DataFrame, and returns it as a JSON response.
However, my dataset contains missing data (NaN). When I convert the DataFrame ...
- reputation score 41
Score of 0
2 answers
128 views
About the Pythonic code on FastAPI and Flask back end
I've done some jobs with the FastAPI or Flask on the backend, but in both situations there was no type of layering of the responsabilities. Like everything was done into the controller layer right ...
- reputation score 21
Score of 1
0 answers
148 views
How to correctly compare two encoded jwt refresh tokens
I using jwt in fastpai app, and when I create access and refresh tokens on user login I also create user session for specific user id in database, so as I understood I need to encrypt refresh token ...
- reputation score 105
Score of -1
1 answer
72 views
FastAPI returns 422 Unprocessable Entity on POST from Next.js fetch despite matching Pydantic model [duplicate]
I'm sending a POST request from a Next.js 14 client to a FastAPI endpoint. The request body matches my Pydantic model exactly, but I keep getting a 422 Unprocessable Entity instead of a 200.
Expected: ...
- reputation score 1
Score of 0
1 answer
115 views
FastAPI StreamingResponse buffers LLM tokens until completion when consumed by Next.js fetch. How can I fix this? [duplicate]
I am building an AI chat feature with a Next.js frontend and a FastAPI backend.
The backend receives tokens from an LLM provider and returns them to the browser using StreamingResponse. My goal is for ...
- reputation score 9
Score of 0
1 answer
223 views
FastAPI Controller/Service/Repo architecture routing with dependency injection
I'm mostly a C# and React dev working on a new project using Python with FastAPI to build the back-end for a tool.
I originally had logic like this in my `main.py` for setting up the fastapi app:
...
- reputation score 203
Score of 0
0 answers
121 views
FastAPI + Azure Functions -> intermittent 401 Unauthorized
I have an Azure Function (with a Flex Consumption plan) using FastAPI, and it has been working well for the last month.
Recently (starting last week), without any apparent reason, we started getting ...
- reputation score 21
