Pass Datetime Data Between MATLAB Compiler SDK and Python

Supported platforms: Windows®, Linux®, Mac

This example shows how to create a Python® application that uses MATLAB® Compiler SDK™ to pass datetime data between Python and MATLAB. The Python script calls two packaged MATLAB functions that work with datetime data from a weather station. When you pass a MATLAB datetime scalar to Python, MATLAB Compiler SDK converts it into a datetime.datetime object.

When you pass a MATLAB datetime array to Python, MATLAB Compiler SDK converts the data into a matlab.object array if NumPy is not available in the Python environment or into a numpy.datetime64 array if NumPy is available in the Python environment. When you pass a Python datetime.datetime or numpy.datetime64 to MATLAB, MATLAB Compiler SDK converts the data into a datetime. For a complete list of data types and their conversions, see Pass Data Between MATLAB and Python.

Prerequisites

Verify that you have a version of Python installed that is compatible with MATLAB Compiler SDK. For details, see MATLAB Compiler SDK Python Target Requirements.

The target machine requires MATLAB Runtime to run the deployed MATLAB code. You can include MATLAB Runtime in an installer for your Python package or install it separately. For details, see Download and Install MATLAB Runtime.

The NumPy package is not required for MATLAB Compiler SDK in general, but the package allows you to convert MATLAB Runtime datetime arrays to Python numpy.datetime64 arrays.

Create MATLAB Function with datetime Scalar Output

Create a MATLAB function that takes a datetime as input, calculates the latest datetime in a datetime array and returns a datetime scalar. Save this function as getLatestDateTime.m.

function latestDateTime = getLatestDateTime(dtArray)
% Given an array of datetimes, return the most recent datetime.
    latestDateTime = max(dtArray);
end

Create MATLAB Function with datetime Array Output

Create a MATLAB function that returns a datetime array. The function takes an integer scalar, a datetime array and an integer array, and returns an array of datetimes corresponding to the k hottest temperatures and the datetime at which the hottest overall temperature occurs. Save this function as getKHottestTimes.m.

function kMaxTempTimes = getKHottestTimes(k, dtArray, tempArray)
% Given an integer 0<k<length(dtArray), an array of datetimes and a 
% corresponding array of temperatures in degrees F at those datetimes, 
% return the k hottest times. If given a value outside this range for 
% k, set k equal to the length of the array.
    if k < 1 || k > length(dtArray)
        k = length(dtArray);
    end
    % Get the k max temperatures.
    % Then, get the corresponding times.
    [~, kMaxTempIdx] = maxk(tempArray, k);
    kMaxTempTimes = dtArray(kMaxTempIdx);
end

Create Python Package from Function

Build the Python package with the Python Package Compiler app or the compiler.build.pythonPackage function.

For example, if you are using compiler.build.pythonPackage, start by getting a list of files with a .m extension in the current directory.

functionfiles = dir('*.m');
Then, save the filenames in a cell array.
functionfiles = {functionfiles.name};
Next, compile the Python package.
buildResults = compiler.build.pythonPackage(functionfiles,'PackageName','datetimeLib');

For details, see the instructions in Generate Python Package and Build Python Application.

Write Python Application Code

Write code in Python for an application named testDatetimeFunctions.py. This sample application contains driver code to test the packaged MATLAB functions.

#!/usr/bin/env python

import datetimeLib

# Import the matlab module only after you have imported
# MATLAB Compiler SDK generated Python modules.
import matlab
import datetime as dt
import numpy as np

try:
    # Initialize the Python module created with MATLAB Compiler SDK.
    my_datetimeLib = datetimeLib.initialize()
except Exception as e:
    print("Error initializing datetimeLib package\\n:{}".format(e))
    exit(1)

try:
    # Create array of datetime data for the past 24 hours
    datetime_list = [
        dt.datetime.strptime(i, "%Y-%m-%d %H:%M")
        for i in [
                "2024-10-30 18:00",
                "2024-10-30 21:00",
                "2024-10-31 00:00",
                "2024-10-31 03:00",
                "2024-10-31 06:00",
                "2024-10-31 09:00",
                "2024-10-31 12:00",
                "2024-10-31 15:00",
                "2024-10-31 18:00"
            ]
        ]
    datetime_arr = np.array([np.datetime64(dt) for dt in datetime_list])
    temps = np.array([67, 64, 62, 60, 58, 61, 70, 75, 79])

    # Call the packaged functions.
    yOut = my_datetimeLib.getKHottestTimes(5, datetime_arr, temps)
    print("The hottest times of day are: " + str(yOut))

    yOut = my_datetimeLib.getLatestDateTime(datetime_arr)
    print("The latest datetime is: " + str(yOut))
    
except Exception as e:
    print("Error occurred during program execution\\n:{}".format(e))

my_datetimeLib.terminate()

The application performs these steps:

  • Imports the datetimeLib, matlab, datetime and numpy packages.

  • Instantiates the datetimeLib instance as my_datetimeLib.

  • Creates a list of datetimes called datetime_list.

  • Converts the list to a datetime64 NumPy array called datetime_arr, which can be used as input for the packaged function.

  • Calls the packaged functions getKHottestTimes and getLatestDateTime.

  • Displays the result.

  • Uses a try block to catch and handle exceptions.

Install and Run Python Package

On the target machine, install the generated Python package. For more details, see Install and Import MATLAB Compiler SDK Python Packages.

In the system command prompt, navigate to the folder containing the generated files and install the Python package.

python -m pip install .

Run the application.

python testDatetimeFunctions.py

The application generates the following output.

The hottest times of day are: ['2024-10-31T18:00:00.000000000' '2024-10-31T15:00:00.000000000'
 '2024-10-31T12:00:00.000000000' '2024-10-30T18:00:00.000000000'
 '2024-10-30T21:00:00.000000000']
The latest datetime is: 2024-10-31 18:00:00

See Also

Topics