Python virtual environment in Matlab

Hi, i tried to run Pyhon code in Matlab by using a virtual environment (venv). If i run from the virtual environment i get an error "Transport stopped"

>> pe2 = pyenv("Version","C:\pyth_test\test3\Scripts\python")

pe2 = 

  PythonEnvironment with properties:

          Version: "3.8"
       Executable: "C:\pyth_test\test3\Scripts\python.EXE"
          Library: "C:\Users\birgerv\AppData\Local\Programs\Python\Python38\python38.dll"
             Home: "C:\pyth_test\test3"
           Status: NotLoaded
    ExecutionMode: OutOfProcess

>> py.print("hello world")
Transport stopped.

if i run

>> pe = pyenv('Version','3.8',"ExecutionMode","OutOfProcess")

pe = 

  PythonEnvironment with properties:

          Version: "3.8"
       Executable: "C:\Users\birgerv\AppData\Local\Programs\Python\Python38\pythonw.exe"
          Library: "C:\Users\birgerv\AppData\Local\Programs\Python\Python38\python38.dll"
             Home: "C:\Users\birgerv\AppData\Local\Programs\Python\Python38"
           Status: NotLoaded
    ExecutionMode: OutOfProcess

>> py.print("hello world")
hello world
>> 

it works. I really need to work in a virtual environment, but can not find out why it is not working.

[Rajeev]

Have you tried this?

pe2 = pyenv("Version", "C:\pyth_test\test3\Scripts\python", "ExecutionMode","OutOfProcess")

[Birger Venås]

yes, same result. "OutOfProcess" is default i think. "InProcess" gives the same result: "Transport stopped".

pe = pyenv('Version','3.8',"ExecutionMode","OutOfProcess")

works in both "OutOfProcess" and "InProcess".

Answer 1

[Rajeev]

This is a known issue that the development team has been notified of.

In the meantime, I have a temporary workaround for your Python interface in MATLAB:

This workaround assumes that:

1. The Python version installation on machine is located at C:\Users\<username>\AppData\Local\Python\python.exe
2. The virtual environment is generated under C:\Users\<username>\venvs\myenv\

Please follow these steps to implement the workaround:

1. Set "pyenv" to the base Python installation that the "venv" is used for creating the virtual environment "myenv" in the MATLAB Command Window. For example:

>> pyenv('Version', 'C:\Users\<username>\AppData\Local\Python\python.exe')

2. Add the site-packages directory of the "myenv" virtual environment to the "py.sys.path" in the MATLAB Command Window. For example:

>> p = py.sys.path

>> p.insert(int32(0), 'C:\Users\<username>\venvs\myenv\Lib\site-packages')

The setting of "py.sys.path" must be done at the beginning of every Python Interface session and it should be set to the libraries under the "myenv" virtual environment.

[Birger Venås]

Thanks! The workaround worked!

[Shino]

I also encountered this issue in R2026a + PY-3.12. What is the root cause of the problem? Hasn't MathWorks fixed it yet?