1. Never delete the issue template, it's there for a reason
2. Using Python.NET from Cython is not supported

Thank you for your answer @filmor.

More generally, is there a way to import a Python.NET module without overriding the Python built-in import function and without adding the imported module to globals() - which can have other side effects than the one I'm describing in Cython?

In order to understand how it works, is there a specific reason for which

import clr
clr.AddReference("abc.dll")

makes the new module ABC ready to be imported as a global variable?

As a comparison with ctypes, we can assign the loaded library into a custom variable name:

mylib_custom_variable_name = cdll.LoadLibrary("mylib.dll")
mylib_custom_variable_name.myfunction()

or to a class-member

self.mylib = cdll.LoadLibrary("mylib.dll")  # not visible in the global variables

Is it a design choice or is there a reason for which it is different in clr? Thanks!

Well, we have landed some improvements a while ago so that the global import is not actually overridden anymore. Instead we now use a PEP302 finder+loader combination since #1369. What you are suggesting wouldn't work, though, because .NET assemblies don't (usually) have a flat namespace (in contrast to C libraries). We could, however, add a function get_namespace to clr or pythonnet that would allow you to take a RuntimeAssembly object as returned from clr.AddReference and get a facade module as you would get from an import:

import clr
assembly = clr.AddReference('abc')
namespace = clr.get_namespace(assembly, 'ABC')

Thank you for your answer @filmor. Is there a way I can test something like this by setting parameters into clr? import clr; clr.options = ... or would this require a new compilation of clr ? (I think I don't have all the .NET compiler requirements to build it)

This was just a suggestion, it would require implementation :)

We only require a .NET6 SDK for compilation nowadays.

Ok @filmor :)
Maybe this small enhancement would allow compilation with Cython? It's probably worth trying!

It is worth trying, but I have neither time to do it nor a need for this. At the very least, you'll have to wait until 3.0 is released.