Create Python Application with Multiple MATLAB Functions

Supported platforms: Windows^®, Linux^®, Mac

This example shows how to create a Python^® application that uses multiple MATLAB^® functions to compute data from a rectangle.

Prerequisites

Verify that you have a version of Python installed that is compatible with MATLAB Compiler SDK™. For details, see MATLAB Supported Interfaces to Other Languages.

This example uses the following files in matlabroot\extern\examples\compilersdk\python\rectangle\:

MATLAB Functions	getPointCoordinates.m getRectangleArea.m getRectangleCorners.m getRectangleHeight.m getRectangleWidth.m makePoint.m makeRectangle.m Point.m Rectangle.m rectangleDemo.m
Python Application Code	rectangleDriver.py

Create and Run Python Application

1. At the MATLAB command prompt, copy the rectangle folder that ships with MATLAB to your work folder.

   copyfile(fullfile(matlabroot,"extern","examples", ...
   "compilersdk","python","rectangle"),"rectangle");

   Navigate to the new rectangle folder in your work folder.

2. Examine the MATLAB function rectangleDemo.m.

   The function creates two Point objects, then creates a Rectangle object using the points as corners. It then calculates and displays data about the rectangle.

   function rectangleDemo()
       % RECTANGLEDEMO Construct a rectangle and print information about it
   
       pointZeroZero = makePoint(0, 0);
       pointThreeFour = makePoint(3, 4);
       rectA = makeRectangle(pointZeroZero, pointThreeFour);
       corners = getRectangleCorners(rectA);
       showPointCoordinates(corners.upperLeft, 'Upper left-hand corner');
       showPointCoordinates(corners.lowerLeft, 'Lower left-hand corner');
       showPointCoordinates(corners.upperRight, 'Upper right-hand corner');
       showPointCoordinates(corners.lowerRight, 'Lower right-hand corner');
       fprintf('Area: %.1f\n', area(rectA));
       fprintf('Height: %.1f\n', height(rectA));
       fprintf('Width: %.1f\n', width(rectA));
   end
   
   % This is an auxiliary function. It cannot be called outside rectangleDemo().
   function showPointCoordinates(pt, desc)
       coordinates = getPointCoordinates(pt);
       fprintf('%s: (%.1f, %.1f)\n', desc, coordinates.X, coordinates.Y);
   end
   

3. Build a Python package named rectangleLib using all of the MATLAB function files in the rectangle folder.

   1. Get the list of files with a .m extension in the current directory.

      functionfiles = dir('*.m')

   2. Save the filenames in a cell array.

      functionfiles = {functionfiles.name};

   3. Compile the Python package using compiler.build.pythonPackage.

      buildResults = compiler.build.pythonPackage(functionfiles,'PackageName','rectangleLib');

      For more details, see Generate Python Package and Build Python Application.

4. Write source code for a Python application that accesses the MATLAB functions.

   The sample application for this example is rectangleDriver.py in the rectangle folder.

    rectangleDriver.py

   # Copyright 2019 The MathWorks, Inc.
   import rectangleLib
   
   def initializeLibrary():
       """ Initialize MATLAB rectangleLibrary library and retrieve a handle to it """
       handle = rectangleLib.initialize()
       return handle
   
   class PyPoint:
       """Python class that uses a MATLAB class compiled with MATLAB Compiler SDK"""
       libHandle = 0
   
       @staticmethod
       def initializeHandle(handle):
           PyPoint.libHandle = handle
   
       # Initialize the point either from an existing Point (not PyPoint) object,
       # or from an X and Y pair.
       def __init__(self, pt=None, X=None, Y=None):
           if pt:
               if X or Y:
                   raise ValueError('If pt is specified, neither X nor Y can be specified')
               else:
                   self.data = pt
           else:
               if not X or not Y:
                   raise ValueError('If pt is not specified, X and Y must be specified')
               else:
                   self.data = PyPoint.libHandle.makePoint(X, Y)
       
       def getCoordinates(self):
           coordinates = PyPoint.libHandle.getPointCoordinates(self.data)
           return (coordinates['X'], coordinates['Y'])
           
   class PyRectangle:
       """Python class that uses a MATLAB class compiled with MATLAB Compiler SDK"""
   
       # Class member that must be initialized before any PyRectangle object is instantiated
       libHandle = 0
       
       @staticmethod
       def initializeHandle(handle):
           PyRectangle.libHandle = handle
       
       # Initialize the point either from an existing Rectangle (not PyRectangle) object,
       # or from the coordinates of any two diagonally opposite corners.
       def __init__(self, rect=None, cornerAX=None, cornerAY=None, cornerBX=None, cornerBY=None):
           if rect:
               if cornerAX or cornerAY or cornerBX or cornerBY:
                   raise ValueError(
                       'If rect is specified, no other keyword argument can be specified')
               else:
                   self.data = rect
           else:
               if not cornerAX or not cornerAY or not cornerBX or not cornerBY:
                   raise ValueError(
                       'If rect is not specified, the other keyword arguments must be specified')
               else:
                   self.data = PyRectangle.libHandle.makeRectangle(
                       PyRectangle.libHandle.makePoint(cornerAX, cornerAY),
                       PyRectangle.libHandle.makePoint(cornerBX, cornerBY))
   
       def area(self):
           return PyRectangle.libHandle.getRectangleArea(self.data)
       
       def height(self):
           return PyRectangle.libHandle.getRectangleHeight(self.data)
           
       def width(self):
           return PyRectangle.libHandle.getRectangleWidth(self.data)
           
       def getCorners(self):
           return PyRectangle.libHandle.getRectangleCorners(self.data)
           
   if __name__ == "__main__":
   
       libHandle = initializeLibrary()
       
       PyPoint.initializeHandle(libHandle)
       PyRectangle.initializeHandle(libHandle)
      
       print('Initializing module and creating a rectangle with corners (-1, 2) and (5, 10)...')
       rectA = PyRectangle(cornerAX=-1, cornerAY=2, cornerBX=5, cornerBY=10)
       print('Area: {0:.1f}'.format(rectA.area()))
       print('Height: {0:.1f}'.format(rectA.height()))
       print('Width: {0:.1f}'.format(rectA.width()))
   
       print('Corners:')
       corners = rectA.getCorners()
       for label in ('upperLeft', 'lowerLeft', 'upperRight', 'lowerRight'):
           pypoint = PyPoint(pt=corners[label])
           print('    {0}: {1}'.format(label, pypoint.getCoordinates()))
   
       print('')
       print('Executing rectangleDemo...')
       # nargout represents the number of output arguments. Its default value
       # is 1. rectangleDemo returns no output, so we need to explicitly set 
       # nargout to 0.
       libHandle.rectangleDemo(nargout=0)
   

   The rectangleDriver application:

   1. Defines two classes, PyPoint and PyRectangle

   2. Creates a handle to the package using rectangleLib.initialize

   3. Passes the package handle to the PyPoint and PyRectangle classes

   4. Creates a PyRectangle object and prints its area, height, and width

   5. Saves each corner as a PyPoint object and prints its coordinates

   6. Calls the rectangleDemo MATLAB function to create and display data from a different rectangle

5. Open a system command prompt window and navigate to the rectangleLibpythonPackage folder that contains your generated package.

6. Install the package using the python command.

   python -m pip install .

   For more details, see Install and Import MATLAB Compiler SDK Python Packages.

7. Navigate up one directory and run the rectangleDriver.py application.

   cd ..
   python rectangleDriver.py

   Initializing module and creating a rectangle with corners (-1, 2) and (5, 10)...
   Area: 48.0
   Height: 8.0
   Width: 6.0
   Corners:
       upperLeft: (-1.0, 2.0)
       lowerLeft: (-1.0, 10.0)
       upperRight: (5.0, 2.0)
       lowerRight: (5.0, 10.0)
   
   Executing rectangleDemo...
   Upper left-hand corner: (0.0, 0.0)
   Lower left-hand corner: (0.0, 4.0)
   Upper right-hand corner: (3.0, 0.0)
   Lower right-hand corner: (3.0, 4.0)
   Area: 12.0
   Height: 4.0
   Width: 3.0
   

   Note

   On macOS, you must use the mwpython script instead of python. For example, mwpython rectangleDriver.py.

   The mwpython script is located in the matlabroot/bin folder, where matlabroot is the location of your MATLAB or MATLAB Runtime installation.