Circular import when importing cylp.cy and submodule(s)

[brandon-avantus]

Description:
Importing cylp.cy or cylp.cy.CyClpSimplex produces an ImportError due to what appears to be a circular import.

Steps to reproduce:

Python 3.11.5 (main, Sep 2 2023, 14:16:33) [GCC 13.2.1 20230801] on linux
>>> import cylp.cy.CyClpSimplex  # or `import cylp.cy`
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "devel/test-cvxpy/venv/lib/python3.11/site-packages/cylp/cy/__init__.py", line 2, in <module>
    from .CyClpSimplex import CyClpSimplex
  File "cylp/cy/CyClpSimplex.pyx", line 1, in init cylp.cy.CyClpSimplex
  File "cylp/cy/CyClpPrimalColumnPivotBase.pyx", line 1, in init cylp.cy.CyClpPrimalColumnPivotBase
  File "cylp/cy/CyClpDualRowPivotBase.pyx", line 1, in init cylp.cy.CyClpDualRowPivotBase
  File "cylp/cy/CyOsiSolverInterface.pyx", line 1, in init cylp.cy.CyOsiSolverInterface
  File "cylp/cy/CyCbcModel.pyx", line 1, in init cylp.cy.CyCbcModel
  File "cylp/cy/CyOsiCuts.pyx", line 3, in init cylp.cy.CyOsiCuts
  File "devel/test-cvxpy/venv/lib/python3.11/site-packages/cylp/py/__init__.py", line 1, in <module>
    from . import pivots
  File "devel/test-cvxpy/venv/lib/python3.11/site-packages/cylp/py/pivots/__init__.py", line 3, in <module>
    from .PositiveEdgePivot import PositiveEdgePivot
  File "devel/test-cvxpy/venv/lib/python3.11/site-packages/cylp/py/pivots/PositiveEdgePivot.py", line 10, in <module>
    from cylp.cy.CyClpSimplex import cydot
ImportError: cannot import name 'cydot' from partially initialized module 'cylp.cy.CyClpSimplex' (most likely due to a circular import) (devel/test-cvxpy/venv/lib/python3.11/site-packages/cylp/cy/CyClpSimplex.cpython-311-x86_64-linux-gnu.so)

Environment:
OS: Manjaro Linux (rolling distribution)
Python: Python 3.11.5 (main, Sep 2 2023, 14:16:33) [GCC 13.2.1 20230801] on linux
cylp: 0.92.1 (binary install from wheel via pip)

[tkralphs]

I can replicate this on both Linux and Windows. I'm a bit mystified, since there wasn't much of a change from 0.91 to 0.92 and I did some testing before making the release. I can replicate this failure now with 615a193, which is just the first commit after the release 0.91.6 (#179). Will need to investigate further. Cc'ing @mkoeppe.

[tkralphs]

The fix for this was apparently rather simple, but the part that I don't understand is why this was never an issue before. That circular import has been there for a long time, but the error only surfaced when switching to Cython 3. I also don't know why it didn't come up in any testing. If tests pass in #190, I should be able to push out a new release that will hopefully fix the issue shortly.

[tkralphs]

@brandon-avantus Can you test? You should be able to download wheels here.

[brandon-avantus]

@tkralphs I can confirm that the new wheels solve the problem. I am able to import without the errors and all my tests are passing on my app. Thank you for the quick turnaround!

[brandon-avantus]

@tkralphs One more request would be to have Windows wheels on PyPI for version 0.92.2. Thanks!

[tkralphs]

Yes, they'll be coming shortly.