12-open-as-principle

An SDK is an architectural principle. Open source is a life principle.

In 2026 I built three Python open-source libraries. Solo, at nights and weekends. MIT licence, no ads, no paywall.

Architectural because your application doesn't have to know that the legacy API calls it "valor" and v1.02 calls it "payment.amount.value". It doesn't have to validate a Portuguese tax ID by hand. It doesn't have to compare XML line by line. There's a layer that does those things — and your app asks only for what it means to do.

Open because the problems these three SDKs solve are concrete Portuguese problems:

→ eupago — payment gateway. Two API generations, three auth methods, Apple Pay sandbox that returns 400, Pay By Link that expires silently.
→ Vendus — AT-certified invoicing. Tax rules you only discover by getting them wrong.
→ xmldiffreport — comparing configurations test → uat → bench → prod when a text diff lies to you about XML.

Official documentation assumes you already know the part nobody tells you. It now lives in my code, my CHANGELOG, the examples, the recipes, the production tests. So the next person doesn't spend weeks discovering the same thing.

Over the next 8 weeks I'll share here the decisions behind each one.
Next Wednesday I start with the page I'm most proud of — a status table.

Sites: eupago.bilouro.com · vendus.bilouro.com · xmldiffreport.bilouro.com

P.S. New tech post every Wednesday.

#OpenSource #Python #SoftwareArchitecture