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IPC between Python backend to a QML GUI

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #4

    What exact issue did you got ?

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    • M Offline
      M Offline
      mertb
      wrote on last edited by
      #5

      On the Application window, the value that was passed from the python is not shown. Instead I see only "..." maybe something else is writing after that but cannot read it exactly. The qml part cannot load the python variable is what I am guessing but I could not manage to get it working

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      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #6

        Something is not clear: are you writing your application in Python ?

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        • M Offline
          M Offline
          mertb
          wrote on last edited by
          #7

          No. I created the app from QT creator using QML. On the GUI that uses the qt quick controls, I have a text box. The content of the text box should be updated with a new value, and the value should come from a seperate python script. On python I create the needed data and keep them as string variables. On QML, I need to access the value of those python strings to update the value with them. For example,
          It says "Temperature: BLABLA" on the GUI, and the temperature data is stored in a seperate python script. How can I simply reach those values that are on the python and present them on qml GUI?

          jsulmJ 1 Reply Last reply
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          • M mertb

            No. I created the app from QT creator using QML. On the GUI that uses the qt quick controls, I have a text box. The content of the text box should be updated with a new value, and the value should come from a seperate python script. On python I create the needed data and keep them as string variables. On QML, I need to access the value of those python strings to update the value with them. For example,
            It says "Temperature: BLABLA" on the GUI, and the temperature data is stored in a seperate python script. How can I simply reach those values that are on the python and present them on qml GUI?

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #8

            @mertb See here: https://doc.qt.io/qt-5/ipc.html
            You can't do IPC with QML as far as I know, so you will need to write also C++ code which communicates with the Python process over IPC and provides the data to QML (https://doc.qt.io/qt-5/qtqml-cppintegration-topic.html).

            https://forum.qt.io/topic/113070/qt-code-of-conduct

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #9

              @mertb said in IPC between Python backend to a QML GUI:

              the temperature data is stored in a seperate python script.

              This concept is not clear. Do you mean your Python scripts is responsible for reading the temperature from some device ?

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              • M Offline
                M Offline
                mertb
                wrote on last edited by
                #10

                Yes, the python code gets the temperature from a device.

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #11

                  In that case why not use something like MQTT to publish the device data ?
                  On the Qt side use the QtMqtt module to subscribe to it.

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                  • M Offline
                    M Offline
                    mertb
                    wrote on last edited by
                    #12

                    Thanks for your replies and interest.
                    MQTT Sounds like a very nice and robust solution, but my project requires using a wired usb connection that can be very easily handled by a library on python. Therefore, I need to keep using python and usb connection. jsulm's advice on using C++ turned out be really easy to implement, so I will probaby do so. I am planning to make python script and C++ that connects via an IPC method. For now I can send out static messages from C++ to my GUI following some tutorials on QT's Youtube.

                    Thanks and have a good day!

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #13

                      If you have now everything in C++, why do you even need IPC ? You can do everything within the same application.

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                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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