4. embed a python function into my Qt App.

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embed a python function into my Qt App.


  • @jsulm i have to include the python library files in order to include Python.h can you please tell me how to specify lib path in QT in order for me to achieve this?

    i am following this tutorial (https://www.codeproject.com/Articles/820116/Embedding-Python-program-in-a-C-Cplusplus-code) now i can include the .h file but linking it with the library i am having some problems as i do not know how to specify the library path as per the tutorial or if you know anyother way this can be achieved please let me know.

    0 1 Reply

  • @vinaygopal
    Which is why I asked as I did at the start! Really wish you had said!

    So you simply want to pass some string filenames to a script which does something, right? No need for integrated scripting.

    You need to tell us what actually happens/goes wrong!

    First just make your Python script print out everything in sys.argv so we can see.

    Oh, I see, you haven't twigged that at all. You can't just write a function in a standalone Python script/program. You need to have a main program in your script, and access argv for the command-line arguments!

    import sys
# Main entry point of app
if __name__ == "__main__":
    # args = sys.argv
    # count = len(sys.argv)
    while i < len(sys.argv):
        arg = sys.argv[i]
        print(arg)

    There are millions of examples on the web.

    Separately, you'd better hope all your commands etc are happy with those / path separators rather than native \. I don't want to debate this again with others: some Windows stuff is happy with /, some is not.

    3 1 Reply
  • Lifetime Qt Champion

    @vinaygopal Please take a look at https://doc.qt.io/qt-5/qmake-variable-reference.html#libs

    2 1 Reply

  • @jsulm i have done the changes

    INCLUDEPATH +="C:\Users\vinay\AppData\Local\Programs\Python\Python37-32\include"

wind32:LIBS += C:/Users/vinay/AppData/Local/Programs/Python/Python37-32/libs

    i have done the changes as per the document my include file works that is python.h is found but it is not able to link to the library as the path specified in the LIBS is a the directory to a bunch of libraries in python. i get this warning at the top of the screen

    "the code model could not parse an input file,which might lead to incorrect code completion"

    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal said in embed a python function into my Qt App.:

    "the code model could not parse an input file,which might lead to incorrect code completion"

    You can ignore this.

    Can you show the exact linker error?

    1 2 Replies

  • This post is deleted!
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  • @jsulm these are the errors i get

    this is my main fail

    #include <QApplication>
#include <QDebug>
#include <Python.h>



int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qDebug()<<"working"<<endl;


    return a.exec();

    these are the errors

    C:\Users\vinay\AppData\Local\Programs\Python\Python37-32\include\pytime.h:6: In file included from ..\..\..\AppData\Local\Programs\Python\Python37-32\include/pytime.h:6:0,

C:\Users\vinay\AppData\Local\Programs\Python\Python37-32\include\Python.h:87: from ..\..\..\AppData\Local\Programs\Python\Python37-32\include/Python.h:87,

C:\Users\vinay\Documents\first_qml_training\example_project\main.cpp:6: from ..\example_project\main.cpp:6:

C:\Users\vinay\AppData\Local\Programs\Python\Python37-32\include\object.h:448: error: expected unqualified-id before ';' token
     PyType_Slot *slots; /* terminated by slot==0. */

                       ^
    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal This is not linker error but compiler.
    Try to include the header like this:

    extern "C"
{
  #include <Python.h>
}
    1 1 Reply

  • @jsulm I tried it and i got the same set of errors however when i tried with the right click and add library method i get this following error

    :-1: error: No rule to make target 'C:/Users/vinay/Documents/first_qml_training/example_project/../../../AppData/Local/Programs/Python/Python37-32/libs/libpython37d.a', needed by 'debug/example_project.exe'.  Stop.
    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal Can you show your pro file?

    1 1 Reply

  • @jsulm

    QT       += core gui networkauth

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = example_project
TEMPLATE = app


# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

CONFIG += c++11

SOURCES += \
        main.cpp \
        google_widget.cpp

HEADERS += \
        google_widget.h

FORMS += \
        google_widget.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

DISTFILES += \
    upload_to_cloud.py


#CONFIG += no_lflags_merge

INCLUDEPATH +="C:\Users\vinay\AppData\Local\Programs\Python\Python37-32\include"



win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/ -lpython37
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/ -lpython37d
else:unix: LIBS += -L$$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/ -lpython37


win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/libpython37.a
else:win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/libpython37d.a
else:win32:!win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/python37.lib
else:win32:!win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/python37d.lib
else:unix: PRE_TARGETDEPS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/libpython37.a
    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal On Windows it should be:

    LIBS += $$PWD/../../../AppData/Local/Programs/Python/Python37-32/libs/python37.lib

    See https://doc.qt.io/qt-5/qmake-variable-reference.html#libs

    2 1 Reply

  • @jsulm i did add the library as you had recomended it still did'nt work and more importantly i figured the module python.h and its equivalent library is not compatible with mingw gcc compiler it is only compatible with microsoft specific compilers as suggested by this question (https://stackoverflow.com/questions/6731100/link-to-python-with-mingw) they have provided an answer but is there a simpler way to get this done?

    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal One question: do you build your app as 64bit? Your Python seems to be 32bit.

    0 1 Reply

  • @jsulm i am building my apps in the 64 bit configuration. shoudl i change it to 32 bit and try building the program again?

    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal said in embed a python function into my Qt App.:

    shoudl i change it to 32 bit

    Yes, you can't mix 32bit and 64bit

    0 1 Reply

  • @jsulm uninstalled python 32 bit and reinstalled 64bit version of python and included the libraries still the same error

    :-1: error: No rule to make target 'C:/Users/vinay/Documents/first_qml_training/example_project/../../../AppData/Local/Programs/Python/Python38/libs/libpython38d.a', needed by 'debug/example_project.exe'. Stop.

    0 1 Reply
  • Lifetime Qt Champion

    @vinaygopal Can you show your current pro file?
    Also did you a clean rebuild?

    0 1 Reply

  • @jsulm yes i clean the build run qmake and then build the file everytime i change the pro file

    #-------------------------------------------------
#
# Project created by QtCreator 2019-11-21T10:31:03
#
#-------------------------------------------------

QT       += core gui networkauth

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = example_project
TEMPLATE = app


# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

CONFIG += c++11

SOURCES += \
        main.cpp \
        google_widget.cpp

HEADERS += \
        google_widget.h

FORMS += \
        google_widget.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

DISTFILES += \
    upload_to_cloud.py


#CONFIG += no_lflags_merge

INCLUDEPATH="C:/Users/vinay/AppData/Local/Programs/Python/Python38/include"
LIBS += $$PWD/../../../AppData/Local/Programs/Python/Python38/libs/python38.lib
    0 1 Reply

  • I'm keeping an eye on this thread. As I said right at the start

    You can indeed go down @jsulm's path, but embedding is a lot more involved than just running a subprocess.
    But as phrased if all you want to do is run an external script with some command-line arguments [...], it really is simple to do with QProcess, should take one minute to write.

    I do hope/presume that (for both your sakes) for use case here all this embedding is indeed required and worth the effort! :)

    1 1 Reply
  • Lifetime Qt Champion

    @vinaygopal Looks correct to me. I would try this:

    • Delete build directory
    • Run qmake
    • build
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  • Moderators

    @vinaygopal how dead set are you on Python as the scripting language?

    If it's not dictated and just a random selection, I'll want to offer 2 alternatives

    https://doc.qt.io/qt-5/qscriptengine.html#details
    and
    https://doc.qt.io/qt-5/qjsengine.html#details

    for QScript and JavaScript respectively, no external libs required

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  • @vinaygopal said in embed a python function into my Qt App.:
    @vinaygopal originally wrote just:

    i want to open up the python script (.py file) and run the python script written by me and exit python. I should be able to pass arguments to the python file through Qt c++? please help me out on how to achieve this. i did do some reading about QProcess class but i am not able to achieve this.

    If that is indeed all he wants to do, he may not need any integrated scripting, he may just need to make his QProcess attempt work and we would be done....

    If he would say why/what the script is supposed to do which requires embedding, we would all know what is required....

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  • @JonB @jsulm @J-Hilk ok alright! i give up on embedding python into my program! it just doesn't seem to work however this is the reason for me to use Python, i have a file in my local desktop and i have to send it to the cloud and make the image uploaded a public image these cases can be easily achieved using python if i have to do it with javascript i will have to do it using node JS which will complicate the app, so from QProcess i am able to open the python file inside the python file i have a function called upload blob and it takes two arguments how do i call this function blob and pass those 2 arguments to them using QProcess().

    My C++ code

        QApplication a(argc, argv);
    qDebug()<<"working"<<endl;
    int result=QProcess::execute("C:/Users/vinay/AppData/Local/Programs/Python/Python38/python.exe",QStringList("C:/Users/vinay/Documents/first_qml_training/example_project/upload_to_cloud.py")<<"C:/Users/vinay/Documents/python folder/player1.png"<<"tank.png");
    qDebug()<<result<<endl;

    My python function

    #!/usr/bin/env python
# -*- coding: utf-8 -*-
from gcloud import storage
import os
os.environ["GOOGLE_APPLICATION_CREDENTIALS"]="C:/Users/vinay/Downloads/My First Example Project-507e91a5b594.json"

def upload_blob(source_file_name, destination_blob_name):
    """Uploads a file to the bucket."""
    bucket_name="example_1995"
    storage_client = storage.Client()
    bucket = storage_client.get_bucket(bucket_name)
    blob = bucket.blob(destination_blob_name)

    blob.upload_from_filename(source_file_name)

    print('File {} uploaded to {}.'.format(
        source_file_name,
        destination_blob_name))
        
print("i am working")

    "

    0 1 Reply

  • @vinaygopal
    Which is why I asked as I did at the start! Really wish you had said!

    So you simply want to pass some string filenames to a script which does something, right? No need for integrated scripting.

    You need to tell us what actually happens/goes wrong!

    First just make your Python script print out everything in sys.argv so we can see.

    Oh, I see, you haven't twigged that at all. You can't just write a function in a standalone Python script/program. You need to have a main program in your script, and access argv for the command-line arguments!

    import sys
# Main entry point of app
if __name__ == "__main__":
    # args = sys.argv
    # count = len(sys.argv)
    while i < len(sys.argv):
        arg = sys.argv[i]
        print(arg)

    There are millions of examples on the web.

    Separately, you'd better hope all your commands etc are happy with those / path separators rather than native \. I don't want to debate this again with others: some Windows stuff is happy with /, some is not.

    3 1 Reply

  • This post is deleted!
    0 1 Reply

  • @vinaygopal
    Why in the world would you try to access sys.argv[4:5] if you have said there 3 arguments?

    Please copy my code and run, then you will see your args are sys.argv[1:3]. You can pass those as appropriate to any functions you write.

    Yes, you are already passing your arguments on the command line from your C++ QProcess::execute() call.

    Please do a little printing/debugging yourself to discover this.

    0 1 Reply

  • @JonB sorry! i wasn't able to understand the code flow i made that comment thank you so much. this was such a fun ride.

    i was able to achieve what i wanted to do. this forum is really helpful.

    Thank you.

    2 1 Reply

  • @vinaygopal
    I am glad we have helped you :)

    Let me say one thing about asking questions here. As I have mentioned, you came in saying "QProcess doesn't work" and then pursued embedding, which as I suspected turned out to be a lot of work. Yet you did not need that, and could have had the QProcess solution in 5 minutes.

    The moral is: it is usually worth explaining here exactly what you are actually trying to achieve in a few words, rather than "how do I embed" or similar-ish (unless you really know what you are talking about!). Often questions like that actually assume the wrong approach. The experts here will see your description and may save you a lot of time by proposing a simple method to achieve your goal.

    2 1 Reply

  • @JonB got it thanks will keep this in mind :)

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