Some machine learning frameworks have problems in PythonAnywhere websites because our web serving framework doesn't allow them to use threads.

If you try to use TensorFlow in a website's code on PythonAnywhere, it probably won't work. The crash is so serious that you probably won't even see anything in the error log -- just a message in the server log saying that your worker processes died.

Unfortunately we don't have a good solution for this if you're using TensorFlow directly :-(

However, if you're using Keras with a TensorFlow backend, you can work around the issue -- just switch to using the Theano backend instead. That has been confirmed to work, but only for Keras up to version 2.3.1. Unfortunately Keras is TensorFlow-only since 2.4.

PyTorch also does some slightly strange threading stuff, and will hang when you call certain functions from websites' code. However, there's a simple solution to that:

import torch
torch.set_num_threads(1)

Many thanks to Eden Canlilar for that solution!