Thank for the reply.
It’s very strange - the python works correctly when I run it locally, and actually when I deploy the app to heroku it builds and streamlit runs correctly with pendulum! It’s only when I run the app locally that it can’t find the pendulum module. Which is bizarre, but I tried again just now and it still can’t find the module when I do “streamlit run app.py” and I get this where I should be getting my app in the browser that opens.
I still think it could be an issue with Streamlit, though likely in how it is interacting with my local machine, as the python and the app on a different (cloud) machine are both working.
Here it is building and running successfully on Heroku: