Why does MATLAB error with "Unable to resolve name" when trying to use Python on a Linux machine?

On RHEL 6.5 Linux machine with Python 3.6.6 installed, I get the following error while using the "py.list" and "pyrun" command:

>> pyenv('Version', '/usr/local/pkg/python/3.6.6/bin/python3.6');
>> py.list({'hi'})

   Unable to resolve name py.list.
>> pyrun("print('Hello World')")

   Error using feval
   Unrecognized function or variable 'py.dict'.

My MATLAB "pyenv" looks like this and I notice that the "Library" field is empty:

>> pyenv
Version: "3.6"
Executable: "/usr/local/pkg/python/3.6.6/bin/python3.6"
Library: ""
Home: "/usr/local/pkg/python/3.6.6"
Status: NotLoaded
ExecutionMode: InProcess

 

Answer 1

[MathWorks Support Team]

On Linux and Mac systems, if the "Library" field is empty in the "pyenv" output, it indicates that Python was installed without the "--enable-shared" option. The Python installation was built without shared libraries enabled, so MATLAB cannot interact with CPython properly. According to this documentation, Python must be built using the "--enable-shared" option:

https://uk.mathworks.com/help/matlab/matlab_external/install-supported-python-implementation.html#buialof-42

Please rebuild the Python executable using the "--enable-shared" option. This way MATLAB will be able to interact with Python through the shared library file, such as "libpython3.6.so.1.0".

After re-installation of Python with the build configured properly, the MATLAB Python Environment should look similar to:

>> pyenv
Version: "3.6"
Executable: "/usr/local/pkg/python/3.6.6/bin/python3.6"
Library: "libpython3.6.so.1.0"
Home: "/usr/local/pkg/python/3.6.6"
Status: NotLoaded
ExecutionMode: InProcess

Note that the "Library" field now contains the library information. And you should now be able to make calls to Python such as the following:

>> py.list({'hello', 'world'})
ans = 
    Python list with no properties.
    ['hello', 'world']