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Getting started with FastAPI

Start accepting x402 payments in your FastAPI server in 2 minutes.
You can find the full code for this example here.

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Step 1: Install dependencies

pip install x402 fastapi uvicorn python-dotenv

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Step 2: Set your environment variables

echo "ADDRESS=0x...\nFACILITATOR_URL=https://facilitator.payai.network" > .env
Your .env file should look like this: 
ADDRESS=0x... # the wallet address you will receive payments on, could be evm or solana
FACILITATOR_URL=https://facilitator.payai.network

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Step 3: Create a new FastAPI app

main.py
import os
from typing import Any, Dict

from dotenv import load_dotenv
from fastapi import FastAPI
from x402.fastapi.middleware import require_payment
from x402.facilitator import FacilitatorConfig
from x402.types import EIP712Domain, TokenAmount, TokenAsset

# Load environment variables
load_dotenv()

# Get configuration from environment
ADDRESS = os.getenv("ADDRESS")
FACILITATOR_URL = os.getenv("FACILITATOR_URL")

if not ADDRESS or not FACILITATOR_URL:
    raise ValueError("Missing required environment variables")

facilitator_config = FacilitatorConfig(
    url=FACILITATOR_URL,
)

app = FastAPI()

# Apply payment middleware to specific routes
app.middleware("http")(
    require_payment(
        path="/weather",
        price="$0.001",
        pay_to_address=ADDRESS,
        network="base-sepolia",
        facilitator_config=facilitator_config,
    )
)

# Apply payment middleware to premium routes
app.middleware("http")(
    require_payment(
        path="/premium/*",
        price=TokenAmount(
            amount="10000",
            asset=TokenAsset(
                address="0x036CbD53842c5426634e7929541eC2318f3dCF7e",
                decimals=6,
                eip712=EIP712Domain(name="USDC", version="2"),
            ),
        ),
        pay_to_address=ADDRESS,
        network="base-sepolia",
        facilitator_config=facilitator_config,
    )
)


@app.get("/weather")
async def get_weather() -> Dict[str, Any]:
    return {
        "report": {
            "weather": "sunny",
            "temperature": 70,
        }
    }


@app.get("/premium/content")
async def get_premium_content() -> Dict[str, Any]:
    return {
        "content": "This is premium content",
    }


if __name__ == "__main__":
    import uvicorn

    uvicorn.run(app, host="0.0.0.0", port=4021)

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Step 4: Run the server

uvicorn main:app --reload
Your server is now accepting x402 payments!

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Step 5: Test the server

You can test payments against your server locally by following the httpx example or the requests example from the x402 repository. Just set your environment variables to match your local server, install the dependencies, and run the examples.

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