Fast · backend

Use Gemini 2.5 Flash with FastAPI

Updated 2026-05-21 · By XALEN

How to use Gemini 2.5 Flash (Fast, ~200B) with FastAPI. Install, authenticate, and make your first API call in minutes. Working code example included.

Model
Gemini 2.5 Flash
~200B · 1M context · $0.015 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="gemini-2-5-flash",
        messages=[m.dict() for m in req.messages]
    )
    return {"reply": response.choices[0].message.content}

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Last updated: 2026-05-21