Matlab Engine for Python: Import Error: cannot import name "double" from "mlarray"

Trying to use Matlab engine for python with pyqtgraph for real-time data display.

The matlab version is R2020b and I am on Windows

I can't post the actual code, but in the python file I am using the engine in, I create an instance of a class and repeatedly call a method that gets data from that class and then I want to plot that data.

I am considering trying this on R2022b if I have no luck with R2020b for this application.

Here is the ful llist of exceptions raised by python, I have removed the first part of the absolute path, but each begins at the root of the python virtual environment directory:

1. Traceback (most recent call last):
2. File "lib\site-packages\pyqtgraph\multiprocess\remoteproxy.py", line 224, in handleRequest
3. opts = pickle.loads(optStr)
4. File "lib\site-packages\matlab\mlarray.py", line 31, in <module>
5. from _internal.mlarray_sequence import _MLArrayMetaClass
6. File "lib\site-packages\matlab\_internal\mlarray_sequence.py", line 3, in <module>
7. from _internal.mlarray_utils import _get_strides, _get_size, \
8. File "lib\site-packages\matlab\_internal\mlarray_utils.py", line 8, in <module>
9. import matlab
10. File "lib\site-packages\matlab\__init__.py", line 24, in <module>
11. from mlarray import double, single, uint8, int8, uint16, \
12. ImportError: cannot import name 'double' from 'mlarray' (lib\site-packages\matlab\mlarray.py)

Answer 1

[Nihal Reddy]

This is likely due to MATLAB Engine not being installed correctly. Please see the below documentation references:

• https://www.mathworks.com/help/releases/R2020b/matlab/matlab_external/install-the-matlab-engine-for-python.html
• https://www.mathworks.com/help/releases/R2020b/matlab/matlab_external/install-matlab-engine-api-for-python-in-nondefault-locations.html

In particular, make sure that you call the installation script with the version of Python you intend to use and that your Python path is updated accordingly.