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QIODevice::read (QProcess): device not open

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  • F Offline
    F Offline
    FoxBandyKoot
    wrote on last edited by FoxBandyKoot
    #6

    So I used your link to place signals. Program start but now I have this error in debbuging mode :

    0_1538904437068_Capture.PNG

    This my code :

    // OPEN XLS FILE
    
        QFile xslFile(file_path);
        xslFile.open(QIODevice::ReadOnly | QIODevice::Text);
    
    
    // EXEC PYTHON SCRIPT
    
    
       // QStringList args = (QStringList() << script_path << employesDesires << file_path) ; // parameters
        QStringList args = (QStringList() << script_path << employesDesires ) ; // parameters
    
        QString program = "Python";                                                         // program
    
        QByteArray p_stdout;
    
        _process.start(program, args );                                 // START PROG
    
        if (_process.waitForStarted()){                                 // Check if python is running
    
            QMessageBox::warning(this,tr("A COMMENCE"), tr("A COMMENCE"));
    
            _process.setReadChannel(StandardOutput);                    // OPEN CHANNEL FOR READ
    
    
            p_stdout = _process.readAllStandardOutput();                // get output
    
        }
    
        _process.closeReadChannel(StandardOutput);                      // Stop read
    
        QMessageBox::warning(this,tr("A FINIT"), tr("A FINIT"));
    
    //    QString AA = QString::QByteArray(p_stdout[0]); // Doesn't exist
    
         ui->labelResult->setText(p_stdout); // display output
    
        if (!_process.waitForFinished()){                               // If process crash, stop it
            return;
        }
    

    This error happens when the following instruction is running :

    p_stdout = _process.readAllStandardOutput();                // get output
    
    1 Reply Last reply
    0
    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #7

      Can you run your application through the debugger to get more details about what is happening ?

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

      1 Reply Last reply
      1
      • F Offline
        F Offline
        FoxBandyKoot
        wrote on last edited by
        #8

        I'm not sure about what you wanna see, so I take so captures :
        BREAK POINT 1
        0_1539111993709_BP1.PNG

        BREAK POINT 2
        0_1539111996219_BP2.PNG

        AFTER BREAK POINT 2
        0_1539112035030_BP3.PNG

        1 Reply Last reply
        0
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #9

          What does the script you launch do ?

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

          1 Reply Last reply
          0
          • F Offline
            F Offline
            FoxBandyKoot
            wrote on last edited by
            #10

            It makes a count of how many times employes choosed have worked together, based on a xlsx file. Finally return this number (that I cast to string before)

            Sorry for faults, I'm not english :/ And thanks you really for taking time to help me ^^

            # version with 1 parameter
            def __main__(employesChoisis):
                total = Tabstats(employesChoisis)
                str(total)
                
                return total
            
            JonBJ 1 Reply Last reply
            0
            • F FoxBandyKoot

              It makes a count of how many times employes choosed have worked together, based on a xlsx file. Finally return this number (that I cast to string before)

              Sorry for faults, I'm not english :/ And thanks you really for taking time to help me ^^

              # version with 1 parameter
              def __main__(employesChoisis):
                  total = Tabstats(employesChoisis)
                  str(total)
                  
                  return total
              
              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by JonB
              #11

              @FoxBandyKoot

              Finally return this number (that I cast to string before)

              This may not be relevant to whatever your problem is, but:

                  total = Tabstats(employesChoisis)
                  str(total)
                  
                  return total
              

              This does not "cast the string before returning as a result". Python str() is a function returning a string. It does not change its argument. Your standalone str(total) line has no side-effects. Your function returns whatever type is returned from Tabstats(). If you need to force-convert return result to a string: return str(total).

              F 1 Reply Last reply
              3
              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #12

                Do you have the same problem if you run a dummy python application ?

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                1 Reply Last reply
                0
                • JonBJ JonB

                  @FoxBandyKoot

                  Finally return this number (that I cast to string before)

                  This may not be relevant to whatever your problem is, but:

                      total = Tabstats(employesChoisis)
                      str(total)
                      
                      return total
                  

                  This does not "cast the string before returning as a result". Python str() is a function returning a string. It does not change its argument. Your standalone str(total) line has no side-effects. Your function returns whatever type is returned from Tabstats(). If you need to force-convert return result to a string: return str(total).

                  F Offline
                  F Offline
                  FoxBandyKoot
                  wrote on last edited by
                  #13

                  @JonB

                  Okay so I changed it, thanks you !

                  @SGaist
                  I created a test.py just for test :

                  def __main__(employesChoisis):
                      
                      
                      return "TEST"
                  

                  Same error :/

                  JonBJ 1 Reply Last reply
                  0
                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #14

                    And if you just start a normal command line tool like dir ?

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    1
                    • F FoxBandyKoot

                      @JonB

                      Okay so I changed it, thanks you !

                      @SGaist
                      I created a test.py just for test :

                      def __main__(employesChoisis):
                          
                          
                          return "TEST"
                      

                      Same error :/

                      JonBJ Offline
                      JonBJ Offline
                      JonB
                      wrote on last edited by
                      #15

                      @FoxBandyKoot
                      The problem is what I see in the debugger output window is happening while you try to run/debug your program, right? You could put messages in/tell us where exactly you receive the warnings as you step through the code....

                      Right, I am now peering at the screenshot code you are using.

                      1. Remove/comment out
                       _process.setReadChannel(StandardOutput);                    // OPEN CHANNEL FOR READ
                          _process.closeReadChannel(StandardOutput);                      // Stop read
                      
                      

                      I am hoping that will get rid of the nasty output?

                      1. Your parent program is intended to read whatever the sub-process sends to its stdout. Yours is sending nothing. You cannot "return a string" like "TEST" from any program, Python or otherwise (you can only return an integer). Your test.py should probably be going print("HELLO") (Python 3), for what you want.
                      1 Reply Last reply
                      1
                      • F Offline
                        F Offline
                        FoxBandyKoot
                        wrote on last edited by
                        #16

                        @SGaist
                        I tried to launch "dir" but nothing is happening

                        0_1539443911364_fea54747-28f1-4369-b3c2-08181888146f-image.png

                        @JonB
                        Yes that's it, when I debug I can see this error, on instruction readAllStandardOutput();
                        And the application crash...

                        0_1539444144651_d52f806f-9b41-4599-9778-c39cd31d1d50-image.png

                        If I'm not in debug mode, program continues... that's really weird
                        And when this instruction happens :

                        ui->labelResult->setText(p_stdout); // display output
                        

                        Nothing appears. I don't understand why I should comment out functions which open and close channels... My true script return henceforth a integer :
                        0_1539444768297_95e358f5-0c6d-4a96-9e72-797e5d36f199-image.png

                        You want me to show you the code that precedes the script?

                        JonBJ 1 Reply Last reply
                        0
                        • F FoxBandyKoot

                          @SGaist
                          I tried to launch "dir" but nothing is happening

                          0_1539443911364_fea54747-28f1-4369-b3c2-08181888146f-image.png

                          @JonB
                          Yes that's it, when I debug I can see this error, on instruction readAllStandardOutput();
                          And the application crash...

                          0_1539444144651_d52f806f-9b41-4599-9778-c39cd31d1d50-image.png

                          If I'm not in debug mode, program continues... that's really weird
                          And when this instruction happens :

                          ui->labelResult->setText(p_stdout); // display output
                          

                          Nothing appears. I don't understand why I should comment out functions which open and close channels... My true script return henceforth a integer :
                          0_1539444768297_95e358f5-0c6d-4a96-9e72-797e5d36f199-image.png

                          You want me to show you the code that precedes the script?

                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by JonB
                          #17

                          @FoxBandyKoot
                          1.

                          I tried to launch "dir" but nothing is happening

                          How do you know "nothing is happening" from such a command? Since you're not collecting the output, what do you expect to see?

                          I don't understand why I should comment out functions which open and close channels...

                          Because I don't think you want them, and I don't think it should be done that way, period. I've never used it and had no problems. Why not try?

                          1. _process.readAllStandardOutput()

                          this function returns all data available from the standard output of the process

                          Since you have only done _process.waitForStarted(), how do you know there is any output yet available to read?

                          1 Reply Last reply
                          1
                          • F Offline
                            F Offline
                            FoxBandyKoot
                            wrote on last edited by
                            #18
                            1. I thinked that I could see content of directory where the script is located in the pyzo interpreter :
                              0_1539508130846_b43f7eff-f3df-4434-9cbf-99218a6986fc-image.png

                            2. So I tried to comment out these functions :

                                    _process.setReadChannel(StandardOutput);                    // OPEN CHANNEL FOR READ
                            
                                    _process.closeReadChannel(StandardOutput);                      // Stop read
                            

                            And the application doesn't crash anymore either in debug mode or not ! But the return value in "p_stdout" is null.

                            1. how do you know there is any output yet available to read?

                            In my new code I try to implement

                            waitForReadyRead and waitForBytesWritten but I don't pass into these functions, I don't know why :/

                            Only waitForStarted return true, so the first readAllStandardOutput happens but return nothing from true script or test script.

                            #include "ui_tabtstatemp_countworktogether.h"
                            
                            #include <QMessageBox>
                            #include <QDebug>
                            
                            TabtStatEmp_CountWorkTogether::TabtStatEmp_CountWorkTogether(QString file_path, QString script_path, QString employesDesires, QWidget *parent) :
                                QDialog(parent),
                                ui(new Ui::TabtStatEmp_CountWorkTogether)
                            
                            {
                            
                                ui->setupUi(this);
                            
                            // OPEN XLS FILE
                                
                                QFile xslFile(file_path);
                                xslFile.open(QIODevice::ReadOnly | QIODevice::Text);
                            
                            
                            // EXEC PYTHON SCRIPT
                            
                            
                               // QStringList args = (QStringList() << script_path << employesDesires << file_path) ; // parameters on final version
                            //    QStringList args = (QStringList() << script_path << employesDesires ) ; // second try with just one parameter
                                QStringList args = (QStringList() << script_path << employesDesires ) ; // first try without parameter
                            
                                QString program = "Python";                                                         // program
                            
                                QString p_stdout;
                            
                                _process.start(program, args );                                 // START PROG
                            
                                if (_process.waitForStarted()){                                 // Check if python is running
                            
                                    QMessageBox::warning(this,tr("Have started"), tr("Have started"));
                            
                            //        _process.setReadChannel(StandardOutput);                    // OPEN CHANNEL FOR READ
                            
                                    p_stdout = _process.readAllStandardOutput();                // get output
                            
                                    if (_process.waitForReadyRead(10000)){                                 // 10 sec to check if data is ready
                                        QMessageBox::warning(this,tr("Data ready"), tr("Data ready"));
                            
                                        p_stdout = _process.readAllStandardOutput();                // get output
                            
                            
                                        if (_process.waitForBytesWritten(10000)){     // 10 sec to check if data is written
                                            QMessageBox::warning(this,tr("Data written"), tr("Data written"));
                            
                                        }
                                    }
                            
                            
                                }
                            
                            //    _process.closeReadChannel(StandardOutput);                      // CLOSE CHANNEL FOR READ
                            
                                QMessageBox::warning(this,tr("Have ended"), tr("Have ended"));
                            
                                ui->labelResult->setText(p_stdout); // display output
                            
                                if (!_process.waitForFinished()){                               // If process crash, stop it
                                    return;
                                }
                            }
                            
                            
                            
                            
                            // DESTRUCTOR
                            TabtStatEmp_CountWorkTogether::~TabtStatEmp_CountWorkTogether()
                            {
                                delete ui;
                            }
                            
                            1 Reply Last reply
                            0
                            • F Offline
                              F Offline
                              FoxBandyKoot
                              wrote on last edited by
                              #19

                              **My first problem has been resolved, so I will close this, and open a topic for my new problem.

                              For future people who come to this topic : The solution for "Device not open" was to use "start function" instead of "execute function".

                              Thank you people for helping me.**

                              1 Reply Last reply
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