How to resolve uWSGI 'no python application found' on PythonAnywhere: broken virtualenv and stdlib import errors in Django

Troubleshoot Django on PythonAnywhere when uWSGI shows 'no python application found'. Resolve stdlib import errors from a broken virtualenv by rebuilding.

Moving a Django app from one host to another is routine until the platform says “Internal Server Error” and your server log claims: “no python application found”. When the same log also shows a ModuleNotFoundError for a standard library module like math during a datetime import, you’re not looking at a typical app misconfiguration — you’re staring at a virtual environment gone bad.

Context

The app runs on PythonAnywhere with Python 3.11 and uWSGI. The error log is empty, but the server log reports the following sequence: the worker starts, uWSGI detects the virtualenv, then crashes with a traceback inside Python’s own datetime module while trying to import math, followed by “unable to load app 0 (callable not found or import error)” and the familiar “no python application found”. The web front-end shows a generic “Internal Server Error”.

A minimal reproduction

Inside the same virtual environment, even a trivial import triggers the failure. A tiny snippet illustrates what’s happening:

try:
    import datetime as dt_unit
    print(dt_unit.datetime.utcnow())
except Exception as problem:
    print(type(problem).__name__, str(problem))

Instead of running, it raises a ModuleNotFoundError for math while importing the standard library datetime module — exactly what the server log shows.

What’s actually failing

uWSGI cannot load the WSGI app because importing the Python standard library fails inside the configured virtual environment. The message “unable to load app 0 (callable not found or import error)” lines up with that, and “no python application found” is simply uWSGI’s follow-up once initialization already failed. The absence of anything in the error log doesn’t contradict this; the server log already contains the critical traceback that stops app startup.

The fix that resolved it

The root cause was the virtual environment itself. Recreating a virtual environment on the same Python version reproduced the issue, but creating one on the next Python version worked. Switching the app to that newer virtualenv cleared the math import error and allowed uWSGI to load the Django application.

Verifying the outcome

After switching to the later Python version’s virtualenv, a quick sanity check confirms that the standard library loads correctly:

import math as mathlib
from datetime import datetime as when
print("stdlib ok:", mathlib.pi, when.utcnow())

With imports behaving normally, uWSGI initializes cleanly and the “no python application found” messages stop.

Why this matters

When a platform reports a generic startup failure, it’s tempting to hunt for Django settings, WSGI path issues, or PYTHONPATH. But if the server log shows a ModuleNotFoundError for standard library modules, the problem sits below your app — in the virtual environment. Recognizing that pattern saves hours of misdirected debugging.

Practical takeaways

Start by checking the server log; it already contains the critical traceback in this scenario. If you can reproduce the failure with a minimal import inside the same virtualenv, treat the environment as suspect. Rebuild it, and if rebuilding on the same Python version still misbehaves, move the app to a virtual environment created with the next Python version available. That was the change that resolved the issue here.

A healthy virtual environment is a prerequisite for everything else in a Django deployment. When stdlib imports fail, fix the environment first — the rest of the stack will follow.