How to generate an invoice PDF in Python (2 clean ways)

#webdev #python #tutorial #api

How to generate an invoice PDF (without the usual pain)

If you've tried to generate an invoice or receipt PDF programmatically, you know
the options are all annoying: low-level PDF drawing, HTML-to-PDF via headless
Chromium (heavy, slow, breaks on fonts), or a bloated reporting library. For a
document, that's overkill.

Here are two clean ways — a few lines of Python, or a single API call.

Option A — one API call (no dependencies)

InvoicePDF takes JSON and returns a PDF. From any language:

curl -X POST https://invoicepdf-app.azurewebsites.net/invoice \
  -H "Content-Type: application/json" \
  -d '{"number":"INV-1","currency":"USD","seller_name":"Me LLC",
       "buyer_name":"Acme Corp",
       "items":[{"description":"Consulting","quantity":8,"unit_price":120}],
       "tax_rate_percent":10}' \
  --output invoice.pdf

That's it — application/pdf comes back. Free tier, no signup to try. There's a
live playground at https://invoicepdf-app.azurewebsites.net where you can edit the JSON and see the PDF.

Option B — pure Python with fpdf2

If you'd rather keep it in-process, fpdf2 is pure Python (no system libs):

from fpdf import FPDF

pdf = FPDF()
pdf.add_page()
pdf.set_font("Helvetica", "B", 20)
pdf.cell(0, 12, "INVOICE", ln=True)
pdf.set_font("Helvetica", size=11)
pdf.cell(0, 8, "Consulting  8 x $120.00 = $960.00", ln=True)
pdf.output("invoice.pdf")

The one thing people get wrong: money math

Do not use floats for money. 0.1 + 0.2 != 0.3 in floating point, and on an
invoice that becomes $29.700000001. Store amounts as integer minor units
(cents), do the math in integers, and format at the end. InvoicePDF does this
internally so totals are always exact.