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  4. Qprocess exiting with exit code 255 when trying to run python script

Qprocess exiting with exit code 255 when trying to run python script

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  • J jsulm
    2 Apr 2024, 06:59

    @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

    Can you please answer my first question?

    "Python interpreter is in the path /usr/bin/python3.exe" - in your code you're using "python" not python3 - is there a "python" executable?

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    Adithya
    wrote on 2 Apr 2024, 07:58 last edited by
    #7

    @jsulm I dont have python.exe , but I have python3.exe .I changed process.start("python", arguments); to process.start("python3", arguments); aswell .I was not getting the log from py file but there was no 255 exit code . But -2 when I used QProcess::execute().

    J 1 Reply Last reply 2 Apr 2024, 07:59
    0
    • J J.Hilk
      2 Apr 2024, 07:00

      @Adithya

      Exit code 255 generally indicates that the program couldn't start. This can happen due to various reasons.

      in this case, I think its a typical case of a wrong path.

      currentPath() should be the location of your generated executable, not your source files.
      Check that QDir::currentPath() + "/Tools/script/main.py" is actually a valid file and the correct file.

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      Adithya
      wrote on 2 Apr 2024, 07:59 last edited by
      #8

      Hi @J-Hilk , This is not the issue path. the py file preset in the specified path

      J 1 Reply Last reply 2 Apr 2024, 08:09
      0
      • A Adithya
        2 Apr 2024, 07:58

        @jsulm I dont have python.exe , but I have python3.exe .I changed process.start("python", arguments); to process.start("python3", arguments); aswell .I was not getting the log from py file but there was no 255 exit code . But -2 when I used QProcess::execute().

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        jsulm
        Lifetime Qt Champion
        wrote on 2 Apr 2024, 07:59 last edited by
        #9

        @Adithya I will ask for the third time (I will stop here if you do not answer): What does https://doc.qt.io/qt-6/qprocess.html#error return?

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

        A 1 Reply Last reply 2 Apr 2024, 08:04
        0
        • J jsulm
          2 Apr 2024, 07:59

          @Adithya I will ask for the third time (I will stop here if you do not answer): What does https://doc.qt.io/qt-6/qprocess.html#error return?

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          Adithya
          wrote on 2 Apr 2024, 08:04 last edited by
          #10

          @jsulm I am getting QProcess::error as "ERROR: QProcess::UnknownError"

          J 1 Reply Last reply 2 Apr 2024, 08:08
          0
          • A Adithya
            2 Apr 2024, 08:04

            @jsulm I am getting QProcess::error as "ERROR: QProcess::UnknownError"

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            jsulm
            Lifetime Qt Champion
            wrote on 2 Apr 2024, 08:08 last edited by
            #11

            @Adithya Then maybe your Python script exits with -2?
            You can also connect a slot to https://doc.qt.io/qt-6/qprocess.html#stateChanged and log state changes.
            And you can also connect slots to https://doc.qt.io/qt-6/qprocess.html#readyReadStandardError and https://doc.qt.io/qt-6/qprocess.html#readyReadStandardOutput and print out stderr/stdout from your process there.

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

            A 1 Reply Last reply 2 Apr 2024, 08:27
            1
            • A Adithya
              2 Apr 2024, 07:59

              Hi @J-Hilk , This is not the issue path. the py file preset in the specified path

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              J.Hilk
              Moderators
              wrote on 2 Apr 2024, 08:09 last edited by
              #12

              @Adithya did you really check, or did you just type this answer ?

              If I had a € for every time I heard "ThE PaTh Is CoRrEcT!!111eleven" and it turns out it's not, because currentPath() or applicationDirPath() etc. did not actually point to the assumed directory, I would have a surprising amount of money :D.

              qDebug() << (QDir::currentPath() + "/Tools/script/main.py");
              

              Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


              Q: What's that?
              A: It's blue light.
              Q: What does it do?
              A: It turns blue.

              A 1 Reply Last reply 2 Apr 2024, 08:20
              0
              • J J.Hilk
                2 Apr 2024, 08:09

                @Adithya did you really check, or did you just type this answer ?

                If I had a € for every time I heard "ThE PaTh Is CoRrEcT!!111eleven" and it turns out it's not, because currentPath() or applicationDirPath() etc. did not actually point to the assumed directory, I would have a surprising amount of money :D.

                qDebug() << (QDir::currentPath() + "/Tools/script/main.py");
                
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                Adithya
                wrote on 2 Apr 2024, 08:20 last edited by
                #13

                @J-Hilk // Path to the Python script you want to execute
                QString pythonScript = QDir::currentPath() + "/Tools/Extractor_OD/main_od_for_rci.py";
                qDebug() << "Script Path = " <<pythonScript;

                Log : Script Path = "/home/adithya/DVT/DVT-3.0/DistanceVerificationTool/Tools/Extractor_OD/main_od_for_rci.py"

                adithya@adithya:~/DVT/DVT-3.0/DistanceVerificationTool/Tools/Extractor_OD$ pwd
                /home/adithya/DVT/DVT-3.0/DistanceVerificationTool/Tools/Extractor_OD
                adithya@adithya:~/DVT/DVT-3.0/DistanceVerificationTool/Tools/Extractor_OD$ ls
                copy_script RCI_Front_LUT.h RCI_Rear_LUT.h src
                main_od_for_rci.py RCI_Left_LUT.h RCI_Right_LUT.h

                I reallt checked multiple time .The oath is not the issue . You are not gettiing the € this time :p

                1 Reply Last reply
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                • J jsulm
                  2 Apr 2024, 08:08

                  @Adithya Then maybe your Python script exits with -2?
                  You can also connect a slot to https://doc.qt.io/qt-6/qprocess.html#stateChanged and log state changes.
                  And you can also connect slots to https://doc.qt.io/qt-6/qprocess.html#readyReadStandardError and https://doc.qt.io/qt-6/qprocess.html#readyReadStandardOutput and print out stderr/stdout from your process there.

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                  Adithya
                  wrote on 2 Apr 2024, 08:27 last edited by Adithya 4 Feb 2024, 08:29
                  #14

                  @jsulm I tried using stateChanged something like this
                  QObject::connect(&process, &QProcess::stateChanged, [](QProcess::ProcessState newState) {
                  qDebug() << "Process = "<< newState;
                  });
                  Log :Process = QProcess::Starting
                  ERROR: QProcess::UnknownError
                  Process = QProcess::NotRunning
                  Failed to start Python process
                  Python script execution failed with exit code: 255

                  J 1 Reply Last reply 2 Apr 2024, 08:33
                  0
                  • A Adithya
                    2 Apr 2024, 08:27

                    @jsulm I tried using stateChanged something like this
                    QObject::connect(&process, &QProcess::stateChanged, [](QProcess::ProcessState newState) {
                    qDebug() << "Process = "<< newState;
                    });
                    Log :Process = QProcess::Starting
                    ERROR: QProcess::UnknownError
                    Process = QProcess::NotRunning
                    Failed to start Python process
                    Python script execution failed with exit code: 255

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                    jsulm
                    Lifetime Qt Champion
                    wrote on 2 Apr 2024, 08:33 last edited by
                    #15

                    @Adithya Please share your current code, so we can see what exactly you're trying now.
                    Also try with an absolute path to the Python executable to make sure that is not the issue.

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

                    A 1 Reply Last reply 2 Apr 2024, 08:43
                    0
                    • A Adithya
                      2 Apr 2024, 06:35

                      @jsulm Hi , the start() exit code is 255 and I am not using execute() . I am trying this in ubuntu 22 qt c++ .Python interpreter is in the path /usr/bin/python3.exe

                      echo $PATH
                      /opt/ros/noetic/bin:/home/adithya/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

                      So ideally python should take from PATH

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                      JonB
                      wrote on 2 Apr 2024, 08:41 last edited by JonB 4 Feb 2024, 08:42
                      #16

                      @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

                      I am trying this in ubuntu 22 qt c++ .Python interpreter is in the path /usr/bin/python3.exe

                      You are under Ubuntu/Linux and the executable you want to run ends in .exe, right? Even though that is for Windows? So you can type /usr/bin/python3.exe in a terminal and that executes fine, right?

                      That aside. Since the Ubuntu executable is indeed python3 why are you trying to start a process named python?

                      #include <QCoreApplication>
                      #include <QDebug>
                      #include <QProcess>
                      
                      int main(int argc, char *argv[])
                      {
                          QCoreApplication a(argc, argv);
                      
                          QProcess process;
                          process.start("python", QStringList());
                          QObject::connect(&process, &QProcess::errorOccurred, &process, [&process]() { qDebug() << process.errorString();  } );
                          if (!process.waitForStarted()) {
                               qDebug() << "Failed to start Python process";
                               return 1;
                           }
                          process.waitForFinished();
                          int exitCode = process.exitCode();
                          if (exitCode != 0) {
                              qDebug() << "Python script execution failed with exit code:" << exitCode;
                              return 1;
                          }
                      
                          return a.exec();
                      }
                      

                      shows me

                      "execvp: No such file or directory"
                      Failed to start Python process
                      

                      So execvp() on python complains No such file or directory under Ubuntu 22.04, as I would expect.

                      Changing to process.start("python3", ...); produces no such error and runs the python3 interpreter....

                      1 Reply Last reply
                      3
                      • J jsulm
                        2 Apr 2024, 08:33

                        @Adithya Please share your current code, so we can see what exactly you're trying now.
                        Also try with an absolute path to the Python executable to make sure that is not the issue.

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                        Adithya
                        wrote on 2 Apr 2024, 08:43 last edited by
                        #17

                        @jsulm
                        //trying it in main funtion itself for now , have commented everything else.
                        main.cpp
                        int main(int argc, char *argv[])
                        {
                        QApplication a(argc, argv);

                        // Path to the Python interpreter
                        QString pythonInterpreter = "/usr/bin/python3.exe"; // or the full path to python.exe
                        
                        // Path to the directory containing your Python script and other files
                        QString workingDirectory = QDir::currentPath() + "/Tools/Extractor_OD";
                        qDebug() << "Path = " <<workingDirectory;
                        
                        // Path to the Python script you want to execute
                        QString pythonScript = QDir::currentPath() + "/Tools/Extractor_OD/main_od_for_rci.py";
                        qDebug() << "Script Path = " <<pythonScript;
                        
                        // Arguments to pass to the Python script
                        QStringList arguments;
                        arguments << pythonScript << "1" << "2";
                        
                        QString command = pythonScript + " 1 2";
                        
                        // Create a QProcess instance
                        QProcess process;
                        
                        QObject::connect(&process, &QProcess::stateChanged, [](QProcess::ProcessState newState) {
                                   qDebug() << "Process = "<< newState;
                           });
                        
                        // Set the working directory
                        //process.setWorkingDirectory(workingDirectory);
                        
                        // Set the command to execute
                        process.start(pythonInterpreter, arguments);
                        
                        QProcess::ProcessError error = process.error();
                        qDebug() << "ERROR: " << error;
                        
                        if (!process.waitForStarted()) {
                             qDebug() << "Failed to start Python process";
                             //return 1;
                         }
                        
                        // Wait for the process to finish (optional)
                        process.waitForFinished();
                        
                        // Get the exit code of the process
                        int exitCode = process.exitCode();
                        
                        // Handle the exit code if needed
                        if (exitCode != 0) {
                            qDebug() << "Python script execution failed with exit code:" << exitCode;
                            //return 1;
                        }
                        return a.exec();
                        

                        }

                        //Have commented out everything just trying to log for now
                        main_od_for_rci.py
                        if name == 'main':
                        print("Hey there")

                        J J 2 Replies Last reply 2 Apr 2024, 08:45
                        0
                        • A Adithya
                          2 Apr 2024, 08:43

                          @jsulm
                          //trying it in main funtion itself for now , have commented everything else.
                          main.cpp
                          int main(int argc, char *argv[])
                          {
                          QApplication a(argc, argv);

                          // Path to the Python interpreter
                          QString pythonInterpreter = "/usr/bin/python3.exe"; // or the full path to python.exe
                          
                          // Path to the directory containing your Python script and other files
                          QString workingDirectory = QDir::currentPath() + "/Tools/Extractor_OD";
                          qDebug() << "Path = " <<workingDirectory;
                          
                          // Path to the Python script you want to execute
                          QString pythonScript = QDir::currentPath() + "/Tools/Extractor_OD/main_od_for_rci.py";
                          qDebug() << "Script Path = " <<pythonScript;
                          
                          // Arguments to pass to the Python script
                          QStringList arguments;
                          arguments << pythonScript << "1" << "2";
                          
                          QString command = pythonScript + " 1 2";
                          
                          // Create a QProcess instance
                          QProcess process;
                          
                          QObject::connect(&process, &QProcess::stateChanged, [](QProcess::ProcessState newState) {
                                     qDebug() << "Process = "<< newState;
                             });
                          
                          // Set the working directory
                          //process.setWorkingDirectory(workingDirectory);
                          
                          // Set the command to execute
                          process.start(pythonInterpreter, arguments);
                          
                          QProcess::ProcessError error = process.error();
                          qDebug() << "ERROR: " << error;
                          
                          if (!process.waitForStarted()) {
                               qDebug() << "Failed to start Python process";
                               //return 1;
                           }
                          
                          // Wait for the process to finish (optional)
                          process.waitForFinished();
                          
                          // Get the exit code of the process
                          int exitCode = process.exitCode();
                          
                          // Handle the exit code if needed
                          if (exitCode != 0) {
                              qDebug() << "Python script execution failed with exit code:" << exitCode;
                              //return 1;
                          }
                          return a.exec();
                          

                          }

                          //Have commented out everything just trying to log for now
                          main_od_for_rci.py
                          if name == 'main':
                          print("Hey there")

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                          jsulm
                          Lifetime Qt Champion
                          wrote on 2 Apr 2024, 08:45 last edited by
                          #18

                          @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

                          /usr/bin/python3.exe

                          This is for sure wrong.
                          You're on Linux, not Windows...

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

                          1 Reply Last reply
                          0
                          • A Adithya
                            2 Apr 2024, 08:43

                            @jsulm
                            //trying it in main funtion itself for now , have commented everything else.
                            main.cpp
                            int main(int argc, char *argv[])
                            {
                            QApplication a(argc, argv);

                            // Path to the Python interpreter
                            QString pythonInterpreter = "/usr/bin/python3.exe"; // or the full path to python.exe
                            
                            // Path to the directory containing your Python script and other files
                            QString workingDirectory = QDir::currentPath() + "/Tools/Extractor_OD";
                            qDebug() << "Path = " <<workingDirectory;
                            
                            // Path to the Python script you want to execute
                            QString pythonScript = QDir::currentPath() + "/Tools/Extractor_OD/main_od_for_rci.py";
                            qDebug() << "Script Path = " <<pythonScript;
                            
                            // Arguments to pass to the Python script
                            QStringList arguments;
                            arguments << pythonScript << "1" << "2";
                            
                            QString command = pythonScript + " 1 2";
                            
                            // Create a QProcess instance
                            QProcess process;
                            
                            QObject::connect(&process, &QProcess::stateChanged, [](QProcess::ProcessState newState) {
                                       qDebug() << "Process = "<< newState;
                               });
                            
                            // Set the working directory
                            //process.setWorkingDirectory(workingDirectory);
                            
                            // Set the command to execute
                            process.start(pythonInterpreter, arguments);
                            
                            QProcess::ProcessError error = process.error();
                            qDebug() << "ERROR: " << error;
                            
                            if (!process.waitForStarted()) {
                                 qDebug() << "Failed to start Python process";
                                 //return 1;
                             }
                            
                            // Wait for the process to finish (optional)
                            process.waitForFinished();
                            
                            // Get the exit code of the process
                            int exitCode = process.exitCode();
                            
                            // Handle the exit code if needed
                            if (exitCode != 0) {
                                qDebug() << "Python script execution failed with exit code:" << exitCode;
                                //return 1;
                            }
                            return a.exec();
                            

                            }

                            //Have commented out everything just trying to log for now
                            main_od_for_rci.py
                            if name == 'main':
                            print("Hey there")

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                            JonB
                            wrote on 2 Apr 2024, 08:48 last edited by JonB 4 Feb 2024, 08:54
                            #19

                            @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

                            QString pythonInterpreter = "/usr/bin/python3.exe"; // or the full path to python.exe

                            You read my answer where it said .exe is for Windows not Linux, didn't you? What happened when you tried my:

                            So you can type /usr/bin/python3.exe in a terminal and that executes fine, right?

                            In a terminal please copy & paste:

                            ls -l /usr/bin/python3.exe
                            

                            and paste the output here.

                            A 1 Reply Last reply 2 Apr 2024, 09:02
                            2
                            • J JonB
                              2 Apr 2024, 08:48

                              @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

                              QString pythonInterpreter = "/usr/bin/python3.exe"; // or the full path to python.exe

                              You read my answer where it said .exe is for Windows not Linux, didn't you? What happened when you tried my:

                              So you can type /usr/bin/python3.exe in a terminal and that executes fine, right?

                              In a terminal please copy & paste:

                              ls -l /usr/bin/python3.exe
                              

                              and paste the output here.

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                              Adithya
                              wrote on 2 Apr 2024, 09:02 last edited by Adithya 4 Feb 2024, 09:04
                              #20

                              @JonB @jsulm using python3 actually worked .But not sure whether the script is being executed or not
                              I changed .py file something like this (running in infinite loop)

                              if name == 'main':
                              while True:
                              print("Hey there")

                              The process is still running
                              Log :
                              Process = QProcess::Starting
                              ERROR: QProcess::UnknownError
                              Process = QProcess::Running

                              But any idea why I am not getting the log .

                              J 1 Reply Last reply 2 Apr 2024, 09:05
                              0
                              • A Adithya
                                2 Apr 2024, 09:02

                                @JonB @jsulm using python3 actually worked .But not sure whether the script is being executed or not
                                I changed .py file something like this (running in infinite loop)

                                if name == 'main':
                                while True:
                                print("Hey there")

                                The process is still running
                                Log :
                                Process = QProcess::Starting
                                ERROR: QProcess::UnknownError
                                Process = QProcess::Running

                                But any idea why I am not getting the log .

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                                jsulm
                                Lifetime Qt Champion
                                wrote on 2 Apr 2024, 09:05 last edited by
                                #21

                                @Adithya said in Qprocess exiting with exit code 255 when trying to run python script:

                                running in infinite loop

                                Please do NOT do such infinite loops in an event driven frameworks like Qt! There is really no need for that and it blocks Qt event loop.
                                "I am not getting the log" - please explain how you're getting this log and what do you actually mean exactly by "log". If you mean the output of your script then I already suggested to read its stderr/stdout.

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

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                                  Adithya
                                  wrote on 2 Apr 2024, 09:13 last edited by
                                  #22

                                  Thanks guys it worked. python3 and readyReadStandardOutput(showed the log ,was expecting it to work like qDebig() and cout .My bad) . Sorry for bothering with wrong misconception.

                                  1 Reply Last reply
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                                  • A Adithya has marked this topic as solved on 2 Apr 2024, 09:13

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                                  2 Apr 2024, 08:41

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