pip install deckle fastapi uvicorn

# main.py
import os
from fastapi import FastAPI
from pydantic import BaseModel
from deckle import Deckle

app = FastAPI()
df = Deckle(os.environ["DECKLE_API_KEY"])


class GenerateRequest(BaseModel):
    html: str
    format: str = "A4"


class InvoiceData(BaseModel):
    company: str
    items: list[dict]
    total: float


@app.post("/api/generate")
def generate_pdf(req: GenerateRequest):
    pdf = df.generate(
        html=req.html,
        options={"format": req.format, "margin": "1in"},
    )
    return {"id": pdf.id, "url": pdf.url, "pages": pdf.pages}


@app.post("/api/invoices/pdf")
def generate_invoice(data: InvoiceData):
    pdf = df.from_template(
        template="tmpl_invoice_v2",
        data=data.model_dump(),
    )
    return {"id": pdf.id, "url": pdf.url, "pages": pdf.pages}

DECKLE_API_KEY=dk_live_... uvicorn main:app --reload

import base64
from fastapi.responses import Response

@app.get("/api/invoices/{invoice_id}/download")
def download_invoice(invoice_id: str):
    # Fetch invoice data from your database
    invoice = get_invoice(invoice_id)

    pdf = df.from_template(
        template="tmpl_invoice_v2",
        data=invoice,
        output="base64",
    )

    content = base64.b64decode(pdf.data)
    return Response(
        content=content,
        media_type="application/pdf",
        headers={"Content-Disposition": f"attachment; filename=invoice-{invoice_id}.pdf"},
    )