Pythonnet dotnet core 'No module named'

Question

I am trying to use a .NET Core library inside a Jupyter Notebook python script by using PythonNet. Support for .NET Core was added recently (see https://github.com/pythonnet/pythonnet/issues/984#issuecomment-778786164) but I am still getting a No module named 'TestAppCore' error.

I don't have an issue using a .NET Framework library with PythonNet, only .NET Core. Any help with diagnosing and fixing the issue would be greatly appreciated.

The C# library I'm trying to get working is a simple class library project with no dependencies at all. Below is the entirety of the code:

namespace TestAppCore
{
  public class Foo
  {
    public int ID { get; set; }
    
    public Foo(int id)
    {
      ID = id;
    }
    
    public int Add(int a, int b)
    {
      return a + b;
    }
  }
}

Here is the python script:

from clr_loader import get_coreclr
from pythonnet import set_runtime

rt = get_coreclr("D:\src\Test.runtimeconfig.json")
set_runtime(rt)

import clr
import sys

sys.path.append(r"D:\src\TestAppCore")
clr.AddReference(r"TestAppCore")

from TestAppCore import Foo

foo = Foo(5)
print(foo.ID)

res = foo.Add(1, 2)
print(res)

Here is the output:

Finally, here is the runtime config I am using:

{
  "runtimeOptions": {
    "tfm": "netcoreapp3.1",
    "framework": {
      "name": "Microsoft.NETCore.App",
      "version": "3.1.0"
    }
  }
}

.NET Core: 3.1
python version: 3.7
pythonnet: 3.0.0.dev1
clr-loader: 0.1.6

score 0 · Answer 1 · answered Dec 09 '21 at 15:00

I suspect that you are getting the DLL path wrong. This worked for me:

from clr_loader import get_coreclr
from pythonnet import set_runtime
set_runtime(get_coreclr("pythonnetconfig.json"))
import clr
clr.AddReference("C:/Path/To/Interface.dll")

from Interface import Foo
foo = Foo()

Using

Python 3.8.10
pythonnet 3.0.0a1
clr-loader 0.1.7

C# DLL (Class Library) targeting .NET Core 3.1

pythonnetconfig.json exactly as you posted.

score 0 · Answer 2 · answered Sep 02 '22 at 14:57

0

I never got it to work with .NET Core 3.1. For me it worked with .NET Framework 4.8 and pythonnet 2.5.2. See my other answer for more details.

answered Sep 02 '22 at 14:57

Roald

2,459
16
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score 0 · Answer 3 · answered Nov 18 '22 at 18:12

I have a similar problem and found out that if the DLL and the namespace are the same, then it fails. In my case, following pythonnet tutorial:

Calculate.sln contains Calc.cs, with

namespace Calculate;  // recommended by VS
class Calc { ... }

Then in Python

clr.AddReference("Calculate") # Assuming sys.path correct setting
from Calculate import Calc

Then: ImportError: cannot import name 'Calc' from 'Calculate' (unknown location)

But with:

namespace CalculateNS;  // different name than Calculate.dll
class Calc { ... }

Then in Python

clr.AddReference("Calculate") # Assuming sys.path correct setting
from CalculateNS import Calc

it works... side effects, pylance known Calculate module but not CalculateNS :-(

Anyone experimented this? I saw lot of answers that have never been tested I guess, only thoughts

Using .NET 6.0 Framework.

Pythonnet dotnet core 'No module named'

3 Answers3

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