How to execute a jit python console using QProcess on win10 ?

Mactarvish

I'm trying to develop a custom GUI command console using QProcess, the main connection code is like this:

    connect(&process, SIGNAL(readyReadStandardOutput()), this, SLOT(PrintStandardOutput()));
    connect(&process, SIGNAL(readyReadStandardError()), this, SLOT(PrintStandardError()));

I used QProcess::start() to start a new process and QProcess::write() to write my subsequent instructions. Now this program can execute most commands like cmd and dir correctly in this way:

// dir some path
process.start("cmd");
process.waitForStarted();
process.write("dir C:\Users\John\n");
// ping a website
process.kill();
process.start("ping www.google.com");
// It also can run an EXISTED python script:
process.start("python C:\Users\John\test.py");

And I can see the execution result in my widget due to the connections above.

But when I tried to execute a python console (not running an existed python script) using

process.start("C:\Users\John\Anaconda3\python.exe");

or

process.start("cmd");
process.waitForStarted();
process.write("C:\Users\John\Anaconda3\python.exe");

I can neither see the python interface (like the input symbol ">>>" ) shown in my GUI. What's the different between python command console and win10 cmd? How can I execute a just in time python console using QProcess or Qt? Thanks in advance.

mrjj

@Mactarvish

Hi
I found this on the net to that allows to have it interactive.
https://stackoverflow.com/questions/48518442/qt-start-process-in-interactive-shell/48518689

Not 100% sure its what you are looking for but it will open a working python shell.


#include <QProcess>
#include <QString>
#include <QStringList>
#include "Windows.h"

class QDetachableProcess
        : public QProcess {
public:
    QDetachableProcess(QObject *parent = 0)
        : QProcess(parent) {
    }
    void detach() {
       waitForStarted();
       setProcessState(QProcess::NotRunning);
    }
};

int main(int argc, char *argv[]) {
    QDetachableProcess process;
    QString program = "cmd.exe";

    QStringList arguments = QStringList() << "/K" << "python.exe";;
    process.setCreateProcessArgumentsModifier(
                [](QProcess::CreateProcessArguments *args) {
        args->flags |= CREATE_NEW_CONSOLE;
        args->startupInfo->dwFlags &=~ STARTF_USESTDHANDLES;
    });
    process.start(program, arguments);
    process.detach();
    return 0;
}

Mactarvish

@mrjj
Thanks for your reply. But actually I want the standard output of python console shown in my GUI instead of recreating a new window. I'm wondering that both cmd and python are interactive consoles, why the cmd interactive interface can be shown in my GUI, but not python?

jsulm

@Mactarvish said in How to execute a jit python console using QProcess on win10 ?:

process.start("C:\Users\John\Anaconda3\python.exe");

Do you really do it like this? You need to escape back-slashes:

process.start("C:\\Users\\John\\Anaconda3\\python.exe");

Mactarvish

@jsulm Hi, as you can see in the image above, I actually used a QLineEdit to type my command, and
"C:\\Users\\John\\Anaconda3\\python.exe"
or
"C:\Users\John\Anaconda3\python.exe"
or just
"python"
can find the correct path of python.exe, but the problem still exists.

JonB

@Mactarvish
There are many possibilities as to why this may or may not be possible, depending on how python.exe behaves with input/output redirection.

I would start with: set your streams to be unbuffered, because there is a chance that output from python is still at the other end, not reaching your application. Easiest is to launch as python -u. (Do not use CMD.)

Secondly/independently, ignore output for now. Verify whether your host can use a write() to send it a python command which it acts upon successfully (e.g. create a file, or something you can test like that).