convert a Python tuple containing string and numerical data types to Matlab

How do I convert the following tuple in python and save it to a "test.mat" file so that I can load and read it in Matlab:

py_tuple = [('cars', 'gm', [['red', 10],['black', 15]]),

('cars', 'ford', ['green',5]),

('cars', 'honda', [])]

[Stephen23]

"How do I convert the following tuple in python and save it to a "test.mat" file so that I can load and read it in Matlab:"

Unless you really enjoy fiddling around with files, why not simply access the data directly from MATLAB?:

L = pyrun("x = [('cars', 'gm', [['red', 10],['black', 15]]), ('cars', 'ford', ['green',5]), ('cars', 'honda', [])]","x")

L = 
  Python list with values:

    [('cars', 'gm', [['red', 10], ['black', 15]]), ('cars', 'ford', ['green', 5]), ('cars', 'honda', [])]

    Use string, double or cell function to convert to a MATLAB array.

L{1}

ans = 
  Python tuple with values:

    ('cars', 'gm', [['red', 10], ['black', 15]])

    Use string, double or cell function to convert to a MATLAB array.

L{2}

ans = 
  Python tuple with values:

    ('cars', 'ford', ['green', 5])

    Use string, double or cell function to convert to a MATLAB array.

L{3}

ans = 
  Python tuple with values:

    ('cars', 'honda', [])

    Use string, double or cell function to convert to a MATLAB array.

etc.

https://www.mathworks.com/help/matlab/matlab_external/ways-to-call-python-from-matlab.html

https://www.mathworks.com/help/matlab/matlab_external/accessing-elements-in-python-container-types.html

Answer 1

[Rajani Mishra]

You can either save the data as

1)Python tuple itself in .mat file. For that you have to create a variable of type “py.tuple()” in MATLAB. For more information refer: https://www.mathworks.com/help/matlab/python-data-types.html?s_tid=CRUX_lftnav

Example:

myTuple = py.tuple({'red',10});
myTuple2 = py.tuple({'cars','gm',tuple});
 

2) Create a cell array with the same elements and store and load it from a mat file. As cell also supports different data types like tuples to be stored. For creating a cell array refer below:

https://www.mathworks.com/help/matlab/ref/cell.html

For saving and loading from a mat file refer to this link: https://www.mathworks.com/help/matlab/matlab_env/save-load-and-delete-workspace-variables.html

Answer 2

[Al Danial]

The SciPy module has a function, savemat, which can write Python variables to MATLAB .m files. Your tuple can be written to test.mat with

from scipy.io import savemat
py_tuple = [('cars', 'gm', [['red', 10],['black', 15]]),
    ('cars', 'ford', ['green',5]),
    ('cars', 'honda', [])]
M = { 'py_tuple' : py_tuple }
savemat('test.mat', M)

Loading test.mat in MATLAB gives

>> t = load('test.mat');
>> t.py_tuple
ans =
3×3 cell array
{'cars'}    {'gm'   }    {2×2×21 char  }
{'cars'}    {'ford' }    {2×21   char  }
{'cars'}    {'honda'}    {0×0    double}

Section 7.14 of Python for MATLAB Development covers reading and writing .mat files to/from Python in detail.