How do I generate Factur-X invoices in Python without Java?

Deploy Factur-X Engine as a Docker container and call its REST API from Python using the standard requests library. Unlike the factur-x PyPI package, Factur-X Engine runs VeraPDF and Saxon-HE as isolated Java subprocesses inside the container — your Python code never touches Java directly. A single POST /v1/convert call with a PDF and JSON metadata returns a compliant Factur-X PDF/A-3 file.

What is the difference between the factur-x Python library and Factur-X Engine?

The factur-x PyPI library (akretion/factur-x) is a pure Python package that embeds XML into PDFs but performs limited schema validation. Factur-X Engine is a self-hosted REST API that adds full EN 16931 Schematron validation via Saxon-HE and PDF/A-3b compliance checks via VeraPDF. Factur-X Engine is language-agnostic and can serve multiple services simultaneously; the PyPI library must be installed per Python project.

Can I use Factur-X Engine in a Python FastAPI or Django application?

Yes. Since Factur-X Engine exposes a standard REST API, any Python web framework can call it with the requests or httpx library. Deploy the engine as a sidecar container alongside your FastAPI or Django app, then call http://localhost:8000/v1/convert from your Python code. No additional Python dependencies are required.

Problem: The "Java Trap"

Generating Factur-X in Python Without Java

Most e-invoicing libraries for Python are just wrappers around Java .jar files (Mustang, Konik). They bring the JVM weight, slow startup times, and supply chain risks.

There is a better way.

Why avoid Java bridges?

The Java Way

Requires installing JRE/JDK in Docker
Slow "Cold Start" (bad for Serverless)
Huge image sizes (>500MB)
Log4j style vulnerabilities

The Factur-X Engine Way

Pure Python + Compiled C/C++
Instant startup (<100ms)< /span>
Tiny footprint (~128MB RAM)
100% Air-gapped (No phone home)

The Solution

Factur-X Engine uses SaxonC (C/C++ XSLT processor) for validation and a optimized Python pipeline for PDF/A-3 generation.

main.py Python

import requests

# 1. Define your invoice data (Pure JSON)
payload = {
    "invoice_number": "FAC-2024-001",
    "profile": "en16931",
    "seller": { "name": "Tech Corp", "country_code": "FR" },
    "buyer":  { "name": "Client Inc", "country_code": "DE" },
    "items":  [{ "name": "Dev Services", "price": 500.0 }]
}

# 2. Call the Engine (No Java needed locally)
response = requests.post(
    "http://localhost:8000/v1/convert",
    files={"pdf": open("template.pdf", "rb")},
    data={"metadata": json.dumps(payload)}
)

# 3. Get compliant PDF/A-3
with open("invoice-fx.pdf", "wb") as f:
    f.write(response.content)

Ready to switch?

Deploy Factur-X Engine