I recently built a Number Classification API as directed in my task, Take a number, classify it as prime, perfect, Armstrong, odd/even, and return a fun fact.
Building it? Smooth.
Deploying it? A different battle entirely.
The Initial Plan
I used Flask for the backend and hosted it on Render (because free tier 😅). Everything was working locally, so I confidently pushed my code and waited for a smooth deployment.
But then...
The Unexpected Errors
The moment my API hit the deployment phase, errors started flying in:
❌ "py: command not found" – Apparently, Render’s environment doesn’t recognize py, so python it is.
❌ "No open ports detected" – Flask was binding to 127.0.0.1 instead of 0.0.0.0, which doesn’t work on a server. Rookie mistake, I’ll own it.
❌ "Your service is live!" (but only locally 😭) – My API was running, but only inside the container, unreachable from the outside world.
At this point, I knew I had two choices: rage-quit or debug. Debugging won.
The Fixes
Here’s how I got everything working:
✅ Explicitly set the port: app.run(host='0.0.0.0', port=int(os.environ.get("PORT", 5000)))
✅ Updated my requirements.txt: A missing dependency was causing silent failures.
✅ Switched to Gunicorn for production: Flask’s built-in dev server isn’t meant for deployment.
After testing, tweaking, and a few deep sighs, I finally saw:
🎉 "Your service is live!"
Lessons Learned
Deployment will always test you—be ready to debug.
Never assume local setups = production setups.
Error messages are clues, not enemies.
Now that my API is up, time to build something even bigger. 🚀
Have you ever had an unexpected deployment struggle? Drop a comment—I’d love to hear your war stories!
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