PyStan import error in a (seemingly) successful installation

I tried to install PyStan on a Mac (OS Catalina) desktop using pip3, installation seems to work, but whe trying to import it I get ModuleNotFoundError: No module named 'pystan'.
it seems unrelated to this thread here on discourse, which seems to be a Windows problem, but I also found a similar error that is fixed by pip-installing “pystan<3” instead, which works. Is this expected?

What python do you use?

What python installation pip3 is referring?

Try this (but replace python with correct call → python3?)

python -m pip install pystan

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The most recent versions of pystan (>= 3) use stan instead of pystan in the import statement, whereas in earlier versions it was just pystan.

If you try import stan after installation, it should hopefully work.


Yes, that’s what was happening, I hand’t used pystan in a while, and wasn’t expecting a name change was the issue (and finding an unsolved issue in a google search misled me into thinking it was something nontrivial).