Open Source · backend

Use DeepSeek V3.1 with FastAPI

Updated 2026-05-21 · By XALEN

How to use DeepSeek V3.1 (Open Source, 685B (37B active)) with FastAPI. Install, authenticate, and make your first API call in minutes. Working code example included.

Model

DeepSeek V3.1

685B (37B active) · 128K context · $0.06 input

Framework

FastAPI

backend · pip install xalen fastapi uvicorn

1. Install

pip install xalen fastapi uvicorn

2. Code

from fastapi import FastAPI
from pydantic import BaseModel
from xalen import XALEN

app = FastAPI()
client = XALEN(api_key="xln_test_YOUR_KEY")

class ChatRequest(BaseModel):
    messages: list

@app.post("/chat")
async def chat(req: ChatRequest):
    response = client.chat.completions.create(
        model="deepseek-v3-1",
        messages=[m.dict() for m in req.messages]
    )
    return {"reply": response.choices[0].message.content}

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Last updated: 2026-05-21