Cannot import name "Category"

asked 2025-08-18 22:39:59 +0200

babushkat
11 ●2

updated 2025-08-19 03:32:39 +0200

Hello! (Tried to post this, told I didn't have enough karma for links, but it's the virasoro algebra from the sagemath documentation, and then the github link for that same site.)

BACKGROUND: I'm attempting to use [the virasoro algebra sagemath stuff]. I literally clicked source (brought me to [the virasoro algebra github page thing] ), and then copy/pasted the source code into a .py file in VS Code running in/on/around WSL:Ubuntu (so that I can use the sage interpreter).

When I import that source file (call it source.py) into another file (call it main.py) and trying to run main.py, I receive an error (see the traceback below). The error is from ~/sage/structure/... files, though, not source.py.

QUESTION: How do I successfully import name Category? Is this a common issue? Do I need to import something else first?

Further Notes/Attempted Solutions, Troubleshooting: The import still fails in the same spot, even if I add from sage.all import * to the preamble.

I installed sage via/with the wsl --install route. I used miniforge3 if that matters. I am not yet technically adept (I am coding-stupid).

There are no other files named sage that could be shadowing the right one.

Compiled extension files (.so / .pyd) do exist for Sage internals. (I used ai for help troubleshooting and it suggested this. I am not entirely sure what it means...)

There are no circular imports; source.py is the only file I'm importing into main.py.

(edited line here ->): I get the error if I run the file in the WSL terminal, too.

Let me know if any other information is needed, and thank you!

Error message: conda run --live-stream --name sage python /home/babushkat/mrns_project/mrns Traceback (most recent call last):

File "/home/babushkat/mrns_project/mrns", line 1, in <module> from Witt_algebra import *

File "/home/babushkat/mrns_project/Witt_algebra.py", line 19, in <module> from sage.categories.lie_algebras import LieAlgebras

File "/home/babushkat/miniforge3/envs/sage/lib/python3.11/site-packages/sage/categories/lie_algebras.py", line 24, in <module> from sage.categories.category import JoinCategory, Category

File "/home/babushkat/miniforge3/envs/sage/lib/python3.11/site-packages/sage/categories/category.py", line 109, in <module> from sage.misc.c3_controlled import _cmp_key, _cmp_key_named, C3_sorted_merge

File "sage/misc/c3_controlled.pyx", line 369, in init sage.misc.c3_controlled (build/cythonized/sage/misc/c3_controlled.c:15760)

File "/home/babushkat/miniforge3/envs/sage/lib/python3.11/site-packages/sage/structure/__init__.py", line 3, in <module> import sage.structure.element

File "sage/structure/element.pyx", line 1, in init sage.structure.element (build/cythonized/sage/structure/element.c:47835)

File "sage/structure/category_object.pyx", line 62, in init sage.structure.category_object (build/cythonized/sage/structure/category_object.c:13626)

ImportError: cannot import name Category

ERROR conda.cli.main_run:execute(127): conda run python /home/babushkat/mrns_project/mrns failed. (See above for error)

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I didn't realize that the virasoro.py was built into sage like that. I'm a novice, like I said.

When I type

from sage.all import *
from virasoro import *

in a new file in my project space, I see this error before I run it ("inline error"?): Import "virasoro" could not be resolvedPylancereportMissingImports. I guess VS Code isn't "seeing" my SageMath installation...?

I don't understand, fully, the relationship between SageMath, Conda, Miniforge, WSL, and VS Code. I know sagemath is (basically) a coding package in python, VS Code is an IDE, and WSL is a way to run Linux without partitioning my hard drive. I know SageMath lives on/in the WSL. In VS Code, I have the WSL extension installed that let 's me, quote, "... use VS Code in WSL just as [I] would from Windows."

And ty!

babushkat ( 2025-08-20 02:50:37 +0200 )edit

If I run conda activate sage and then sage -python -c "from sage.algebras.lie_algebras import virasoro; import inspect; print(inspect.getsourcefile(virasoro))" in the command prompt-looking ubuntu terminal thing (what do I call this? WSL Terminal?), I get the same traceback error list ending with cannot import name Category.

Wait,

from sage.all import *
from sage.algebras.lie_algebras.virasoro import *

WORKS. It does not, presumably, fail to import category. Why is this? If I run the same from virasoro import * in the WSL terminal, it also says no module named 'virasoro'.

And thank you so very much for your help. I appreciate you tremendously!

babushkat ( 2025-08-20 03:05:00 +0200 )edit

from virasoro import * works when there is a file named virasoro.py in the same directory (that's how I named my copy of the file). And yes, from sage.all import * (or just import sage.all?) is a way to trigger some setup needed for SageMath when it's used from Python. I don't know exactly why it works, I treat it as a magic incantation. I'm glad you got it working!

rburing ( 2025-08-20 10:36:40 +0200 )edit

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