Make sure you are running your app with the debug flag properly set. Use the environment variable. It enables the reloader and the debugger automatically.
Python programming code – Python Programming | Boost Skills From Basics to Advanced
$ export FLASK_APP=app.py
Well, I have to admit — I used to hate Docker. But I've been rethinking my strategy lately. Actually, I should clarify: Docker has a reputation problem, and it's partly deserved. But after the absolute mess that was the Python logging vulnerability (CVE-2025-27607) discovered earlier this year, I've stopped blindly trusting my logs. And when a core library we've used for a decade turns out to be an RCE vector because it didn't handle formatted strings correctly, you have to rethink your approach. We can't just dump request.data into a logger anymore and hope for the best.
If you write Flask apps, you know this pain. You also probably know the dirty secret of how most of us debug: we sprinkle print() statements everywhere like we're throwing confetti at a funeral. But here's the thing — I'm cleaning up my act. I'm moving away from "log and pray" to actual, interactive debugging. And I'm not the only one. This problem deserves more attention than it gets.
Make sure you are running your app with the debug flag properly set. Use the environment variable. It enables the reloader and the debugger automatically.
Python programming code - Python Programming | Boost Skills From Basics to Advanced
$ export FLASK_APP=app.py
Frequently asked questions
How do I enable Flask's debugger and auto-reloader properly?
Run your Flask app with the debug flag set via an environment variable rather than toggling it inline. Exporting FLASK_APP=app.py and using the debug environment variable enables both the interactive debugger and the automatic reloader at the same time. This gives you a proper debugging setup without having to manually restart the server or wire up debugger hooks every time your code changes.
What is CVE-2025-27607 and why does it affect Python logging?
CVE-2025-27607 is a Python logging vulnerability discovered earlier in 2025 that turned a core library used for a decade into a remote code execution vector. The root cause was improper handling of formatted strings inside the logger. Because of this flaw, developers can no longer safely dump raw request.data into their logs and assume the output is benign — the logger itself became the attack surface.
Why should I stop using print statements to debug Flask apps?
Sprinkling print() statements across a Flask codebase is the default debugging habit, but it's essentially log-and-pray development — throwing confetti at a funeral, as the article puts it. It doesn't give you stack context, variable inspection, or step-through control. Moving to actual interactive debugging with Flask's built-in debugger is a cleaner, more reliable way to diagnose issues than scattering prints everywhere and re-reading output.
Is Docker worth using for Flask development despite its reputation?
Docker has a reputation problem that's partly deserved, and plenty of developers — the author included — used to hate it. But rethinking that strategy is worthwhile, especially after security incidents like the Python logging CVE forced a rework of how requests and logs are handled. Docker's isolation and reproducibility become more valuable once you stop blindly trusting your logs and start taking your debugging environment seriously.
