FastAPI Stripe Checkout

app.py

"""
Based off Stripe's checkout repo, see the link for the Flask analogue. 

https://github.com/stripe-samples/checkout-one-time-payments/blob/master/server/python/server.py

Assumes project is structured like:

    src/
        backend/
            app.py
        frontend/
            build/
            ...
"""


import os
from typing import List, Optional

import stripe
from fastapi import Cookie, FastAPI, Header, HTTPException, Request
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse
from pydantic import BaseModel

app = FastAPI()
app.mount("/static/", StaticFiles(directory="../frontend/build/static"), name="static")

stripe.api_key = os.getenv("STRIPE_SECRET_KEY")
stripe.api_version = os.getenv("STRIPE_API_VERSION")


class StripeEvent(BaseModel):
    address: str
    balance: int
    created: int
    data: dict


@app.get("/api/config")
def get_publishable_key():
    price = stripe.Price.retrieve(os.getenv("POSTER_PRICE"))
    return {
        "publicKey": os.getenv("STRIPE_PUBLISHABLE_KEY"),
        "unitAmount": price["unit_amount"],
        "currency": price["currency"],
    }


@app.post("/api/create-checkout-session/{posterID}")
def create_checkout_session(posterID: str, userID: str = Cookie(None)):
    domain_url = os.getenv("DOMAIN") or "http://localhost:3000"
    album_price = os.getenv("POSTER_PRICE")

    try:
        checkout_session = stripe.checkout.Session.create(
            success_url=domain_url
            + "/order-confirmation?session_id={CHECKOUT_SESSION_ID}",
            cancel_url=domain_url + "/create-poster",
            client_reference_id=userID,
            payment_method_types=["card"],
            mode="payment",
            metadata={"poster_id": posterID},
            line_items=[{"price": album_price, "quantity": 1}],
        )
        return {"sessionId": checkout_session["id"]}
    except Exception as e:
        raise HTTPException(status_code=403, detail=str(e))


@app.post("/webhook")
async def webhook_received(
    event: dict,
    request: Request,
    stripe_signature=Header(None),
):
    webhook_secret = os.getenv("STRIPE_WEBHOOK_SECRET")
    raw_body = await request.body()

    try:
        event = stripe.Webhook.construct_event(
            payload=raw_body,
            sig_header=stripe_signature,
            secret=webhook_secret,
        )
    except Exception as e:
        raise HTTPException(422, detail=str(e))

    data = event["data"]["object"]
    if event["type"] == "checkout.session.completed":
        # your custom function to run after a successful payment
        print('Succesful checkout')

    return 200


@app.get("/{full_path:path}", response_class=FileResponse)
def index(request: Request, full_path: str):
    path = ".././frontend/build/index.html"
    return FileResponse(path)

Accept payments with Stripe Checkout

This sample shows you how to integrate a FastAPI backend with Stripe Checkout. See https://github.com/stripe-samples/checkout-one-time-payments for the original Flask demo repository.

Building a payment form UI from scratch is difficult -- input field validation, error message handing, and localization are just a few things to think about when designing a simple checkout flow.

Stripe built Checkout to do that work for you so you can focus on building the best storefront experience for your customers. Once your customer is ready to pay, use Stripe.js to redirect them to the URL of your Stripe hosted payment page. 🥳