Pylance causes a huge CPU load

[barthemius]

Environment data

• Language Server version: 2021.6.0
• OS and version: macOS Big Sur 11.4 (20F71)
• Python version (and distribution if applicable, e.g. Anaconda): Python 3.8.8 x64 Anaconda

Expected behaviour

Pylance swiftly analyses the code and highlights the variables (just like week ago).

Actual behaviour

A process called 'Code Helper (Renderer)' uses >100% of CPU for approx 30-50 seconds. I tracked it by PID and unfortunately Pylance is the culprit, switching to a different language server is a remedy.
About the problem - every little change in the code triggers the whole process again. Variable name colouring update takes like a minute.
This issue might be related to #1368 reported by xmatthias. However there, he described the problem occurring in the big project. Here the file I am working on is a short, merely 50 line python script. Additionally I run on a different OS.

What surprises me the most, using older versions of Pylance didn't work at all. I somehow relate this bug to the recent macOS update, but I don't know if it is relevant.

I guess the description I've given might be a bit vague, as I am not familiar with bug reporting like this. However I will happily answer any questions you might have.

Logs

For convenience, I put the log in the attachment.
pylance_problem.log

[jakebailey]

It appears as though this is sympy, which has some known performance holes and will need some stubs.

[barthemius]

It appears as though this is sympy, which has some known performance holes and will need some stubs.

Yup, you're absolutely right! I uninstalled sympy and it works fine right now. Too bad I need sympy for my research... :(

[erictraut]

As a potential workaround, you could create a dummy type stub for sympy. This approach should eliminate the large CPU usage, but the tradeoff is that you won't get any completion suggestions for sympy.

To do this, create a file in your project called typings/sympy/__init__.pyi. Within that file, paste the following:

from typing import Any

def __getattr__(name: str) -> Any: ...

This will tell pylance that it shouldn't attempt to infer any type information from the sympy library.

[barthemius]

That should do the trick, at least for now. Thank you Eric!

[jakebailey]

Dupe of #1388.

[mjpieters]

@jakebailey you closed this as a duplicate of itself, did you mean to do that? Looking at the history, I think you meant to reference #946 instead?

[jakebailey]

Yes, my mistake! Copy paste always gets me.