how to handle input parameters in QProcess

Question

The following simple python code requires three input arguments for 'test.py' (besides 'python' and 'test.py') in command line:

#!/usr/bin/python
import sys

def main(argv):
   if (len(sys.argv) < 4):
       print ('argv must be greater than 4')
   else:
     print ('Number of arguments:', len(sys.argv), 'arguments.')
     print ('Argument List:', str(sys.argv))

if __name__ == "__main__":
   main(sys.argv[1:])

Run test.py:

C:\>python test.py arg1 arg2
argv must be greater than 4

C:\>python tt.py arg1 arg2 arg3
Number of arguments: 4 arguments.
Argument List: ['tt.py', 'arg1', 'arg2', 'arg3']

I use the following simple Qt code, but it fails to produce the above result. Is there a way in Qt to mimic the above command line, i.e. 'python command arg1, ... argN'. NOTE: 'python' must be used in this case.

   QProcess *qtq = new QProcess();
   QString program("python");
   QStringList arguments("test.py arg1 arg2 arg3");
   qtq->setProgram(program);
   qtq->setArguments(arguments);
   qtq->start();
   qtq->waitForReadyRead();
   qtq->waitForFinished();
   QByteArray s =  qtq->readAll();
   qDebug() << s;

How you know it fails? whats the error or unexpected behavior? — Mohammad Kanan
– Mohammad Kanan, Commented May 15, 2018 at 17:13
QStringList arguments({"test.py" ,"arg1" ,"arg2", "arg3"}); — Mohammad Kanan
– Mohammad Kanan, Commented May 15, 2018 at 18:02
@MohammadKanan The parentheses are unnecessary: QStringList arguments{"test.py", "arg1", "arg2", "arg3"}; — Kuba hasn't forgotten Monica
– Kuba hasn't forgotten Monica, Commented May 16, 2018 at 2:29

docsteer · Accepted Answer · 2018-05-15 17:34:49Z

1

QStringList arguments("test.py arg1 arg2 arg3");

That is your problem line. That will create a QStringList with only one string in it, which gets passed as one argument to python. You should instead do:

QStringList arguments;
arguments << QString("test.py");   
arguments << QString("arg1");
arguments << QString("arg2");
arguments << QString("arg3");

answered May 15, 2018 at 17:34

docsteer

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