Hi Marc,
Since your simple_script.m contains only an assignment statement, it is not returning anything to the python. In my opinion, this is the expected behaviour, since assignment operator does not return anything.
When you create a function out of the script, it will return a value if the function that you have created returns a value.
The error Undefined function 'sqrt' for input arguments of type 'int64' that you are facing is probably because you might have initialized the value of x to 4 instead of 4.0 in the code given in the following MathWorks documentation.
https://www.mathworks.com/help/matlab/matlab_external/use-the-matlab-engine-workspace-in-python.html
You can use a floating type value like 4.0 and the error should get resolved.
I hope this helps.
