This is a recurrent question on StackOverflow and I have browsed the history of them. Alas none of those answers apply to the problem I have at hand (I’m an old hand at PyDev and have done this many times), which is that I get the standard warning, which provides the standard run request:

0.10s - warning: Debugger speedups using cython not found. Run '"E:VenvTestingScriptspython.exe" "E:UtilityEclipsedropinsPyDev.11.0.3pluginsorg.python.pydev.core_11.0.3.202310301107pysrcsetup_pydevd_cython.py" build_ext --inplace' to build.
pydev debugger: starting (pid: 2484)

And then I run the command suggested and it completes successfully and without complaint:

(Testing) E:>"E:VenvTestingScriptspython.exe" "E:UtilityEclipsedropinsPyDev.11.0.3pluginsorg.python.pydev.core_11.0.3.202310301107pysrcsetup_pydevd_cython.py" build_ext --inplace
running build_ext
copying buildlib.win-amd64-cpython-312_pydevd_bundlepydevd_cython.cp312-win_amd64.pyd -> _pydevd_bundle

Yet the complaint is still present on every debug run. It’s not gone away.

Now that is a puzzle. It has always worked as it should in past, over many versions of PyDev and on many platforms I’ve used.

Aside: I am using 11.0.3 because 12.0.0 (which is released) is not available:

https://github.com/fabioz/Pydev/releases/download/pydev_12_0_0/

But I was probably using 11.0.3 on this very PC before the rebuild (I’m reinstalling after a rebuild of my PC post a nasty malware infection, gotta love Windoze).