Difference between revisions of "Qt for Python/GettingStarted"

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[[Category:Pythonic]]
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[[Category:Qt for Python]]                                                                                                                              
== Considerations before starting ==
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== Official documentation ==
  
PySide2 supports Python 2 (recommended: 2.7 onwards, Compatibility module ''six'' installed) and Python 3 (recommended: 3.5 onwards).  
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Refer to the [https://doc.qt.io/qtforpython/gettingstarted.html official docs] to start building and using Qt for Python.
  
On Windows, it is recommended to use Python 3 and build with MSVC2015. Python 2 requires building with MSVC2008.
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== Using Qt Creator as a project explorer ==                                      
 
 
Currently, only Qt 5.6 is supported. Qt needs to be build with the ''QtXmlPatterns'' module.
 
 
 
=== Development ===
 
 
 
Development happens in the dev branches of the [http://code.qt.io/cgit/pyside/pyside-setup.git/ repositories]. The top level repository has several submodules:
 
* sources/shiboken2: [http://code.qt.io/cgit/pyside/shiboken.git/ Shiboken Parser]
 
* sources/pyside2: [http://code.qt.io/cgit/pyside/pyside.git/ PySide 2]
 
* sources/pyside2-examples: [http://code.qt.io/cgit/pyside/examples.git/ Examples]
 
* sources/pyside2-tools: uic, rcc
 
* wiki: Wiki
 
 
 
Contributions follow the [[Qt_Project_Guidelines|standard process]].
 
 
 
Building requires [https://cmake.org/ CMake].
 
 
 
It is helpful to have debug binaries and/or symbols for Python available. On Windows, this is done choosing ''Customized Installation'' when installing python and ticking the respective check boxes. On Linux, debug packages can be installed in addition. For Ubuntu, the packages python3-dbg, libpython3-dbg provide a debug binary python3-dbg.
 
 
 
It is also recommended to use a [http://docs.python-guide.org/en/latest/dev/virtualenvs/ Virtual Environment] for testing to be able to always start from a clean base and avoid issues with write permissions in installations.
 
 
 
On Linux, the command
 
virtualenv -p /usr/bin/python3-dbg testenv
 
creates a Virtual Environment named ''testenv'' for debugging purposes. On Windows, an installation step may be required:
 
python -m pip install virtualenv
 
python -m virtualenv testenv
 
 
 
The Virtual Environment is activated by
 
  source testenv/bin/activate
 
or
 
CALL testenv\Scripts\activate.bat
 
 
 
=== Building PySide2 ===
 
 
 
The script ''setup.py'' in the [http://code.qt.io/cgit/pyside/pyside-setup.git/ top level repository] is used to build and install the PySide2 package. It takes a mode argument (''build'' or ''install'') and several options.
 
 
 
Required options:
 
* --qmake=<binary> Path to ''qmake'' of the Qt library to be used
 
* --cmake=<binary> Path to ''cmake''
 
 
 
Further options of interest:
 
* --ignore-git: Prevents ''setup.py'' from cloning and checking out the submodules.
 
* --build-tests: Creates a directory containing the tests along with some helper packages
 
* --debug: Build in Debug mode
 
* --reuse-build: Rebuilds only modified files (currently does not work for typesystem xml files)
 
* --openssl: Path to OpenSSL
 
 
 
A typical invokation looks like:
 
setup.py install ---ignore-git --build-tests --qmake=../bin/qmake --cmake=/usr/bin/cmake
 
 
 
A successful build can be tested by running an example:
 
  python sources/pyside2-examples/examples/widgets/tetrix.py
 
 
 
=== Building the Documentation ===
 
 
 
This is currently unexplored terrain [https://bugreports.qt.io/browse/PYSIDE-363 PYSIDE-363].
 
* The sources are in pyside2/doc
 
* libXML2 and libXSLT should be present when building PySide2 (Ubuntu: apt-get install libxml2-dev libxslt1-dev)
 
* graphviz + dot should be installed
 
* QT_SRC_DIR needs to be set
 
* sphinx should be installed (pip install sphinx)
 
* qdoc3 is used to generate it
 
 
 
=== Using Qt Creator as a project explorer ===
 
 
Qt Creator 4.0+ can be used to open the PySide and Shiboken CMakeLists.txt files as projects, and thus provide usual IDE features for developing PySide - project file navigation, code completion (C++ only), following symbols under cursor (C++ only), syntax highlighting, locator usage, debugging, etc.
 
Qt Creator 4.0+ can be used to open the PySide and Shiboken CMakeLists.txt files as projects, and thus provide usual IDE features for developing PySide - project file navigation, code completion (C++ only), following symbols under cursor (C++ only), syntax highlighting, locator usage, debugging, etc.
 +
                                                                                   
 +
Currently, there is a limitation that Shiboken has to be built first using the terminal because the installed shiboken CMake packages will have to be specified for the PySide project in Qt Creator.
  
Currently there is a limitation that Shiboken has to be built first using the terminal, because the installed shiboken CMake packages will have to be specified for the PySide project in Qt Creator.
+
The steps for opening the projects in Qt Creator are:                              
 
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# Open '''pyside-setup/sources/shiboken2/CMakeLists.txt''' and specify a 5.12+ Qt Kit to be used
The steps for opening the projects in Qt Creator are:
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# Build the project as usual (by pressing the '''build''' icon for instance)              
# Open pyside-setup/sources/shiboken2/CMakeLists.txt, and specify a 5.6 Qt Kit to be used
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# Open '''pyside-setup/sources/pyside2/CMakeLists.txt''' and specify the same 5.12+ Qt Kit
# Build the project as usual (by pressing the build icon for instance)
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# Go to the projects tab, and under the Build / CMake section find the Shiboken2_DIR setting. You have to specify the path to the folder where the Shiboken CMake package was installed when you compiled Shiboken from the terminal·
# Open pyside-setup/sources/pyside2/CMakeLists.txt, and specify the same 5.6 Qt Kit
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# An example path under macOS is '''/Users/user/Dev/pyside2-setup/pyside_install/py3.6-qt5.12.1-64bit-debug/lib/cmake/Shiboken2-2.0.0'''. The path has to be adjusted depending on the user folder name, the version of python and qt, etc
# Go to projects tab, and under the Build / CMake section find the Shiboken2_DIR setting. You have to specify the path to the folder where the Shiboken CMake package was installed when you compiled Shiboken from the terminal
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# (Optional) On MacOS you also have to set the '''ALTERNATIVE_QT_INCLUDE_DIR''' setting to the Qt kit include path (e.g. '''/Users/user/Dev/qt511_source/include''')                                                                                                                                                                                                                                                                                                                                  
# An example path under MacOS is /Users/user/Dev/pyside2-setup/pyside_install/py2.7-qt5.6.1-64bit-debug/lib/cmake/Shiboken2-2.0.0. The path has to be adjusted depending on the user folder name, the version of python and qt, etc
 
# (Optional) On MacOS you also have to set the ALTERNATIVE_QT_INCLUDE_DIR setting to the Qt kit include path (e.g. /Users/user/Dev/qt56_source/include)
 
 
# Apply the CMake configuration changes (by pressing the button), and you should be able to build PySide
 
# Apply the CMake configuration changes (by pressing the button), and you should be able to build PySide
 +
                                                                                   
 +
Now you can use the project explorer to look through the source cpp files, python files, use the locator feature to open files and file classes / methods, and other features that Qt Creator provides.
  
Now you can use the project explorer to look through the source cpp files, python files, use the locator feature to open files and file classes / methods, and other features that Qt Creator provides.
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== Troubleshooting / Known Issues ==
 +
                                                                                   
 +
* Qt 5.9 does not work with OpenSSL 1.1                                       
 +
** When doing a custom Qt build (some unspecified versions for now), It is necessary to have an OpenSSL version of 1.0.x, since there are compatibility issues with newer versions of OpenSSL ([https://wiki.openssl.org/index.php/OpenSSL_1.1.0_Changes#Qt see details])
 +
* PySide2 looks at the system installation if the local Qt version does not have a required module
 +
**The only workaround is to uninstall any module from the system, then PySide2 can look at only the Qt path currently being use.
 +
* Qt packages that directly link to OpenSSL (as opposed to runtime discovery) are not currently supported.
 +
* Make sure that the Python environment location where the PySide2 package will be installed is writable (otherwise you might get various permission denied errors). The install location can be found with 99% probability by running:
 +
python -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())"
 +
* Building failing because graphviz wasn't found. If you're using pyenv and installed it using pip, try to install it using your package manager:<syntaxhighlight>
 +
dnf install graphviz.x86_64 #Fedora
 +
</syntaxhighlight>

Latest revision as of 11:53, 20 March 2020

Official documentation

Refer to the official docs to start building and using Qt for Python.

Using Qt Creator as a project explorer

Qt Creator 4.0+ can be used to open the PySide and Shiboken CMakeLists.txt files as projects, and thus provide usual IDE features for developing PySide - project file navigation, code completion (C++ only), following symbols under cursor (C++ only), syntax highlighting, locator usage, debugging, etc.

Currently, there is a limitation that Shiboken has to be built first using the terminal because the installed shiboken CMake packages will have to be specified for the PySide project in Qt Creator.

The steps for opening the projects in Qt Creator are:

  1. Open pyside-setup/sources/shiboken2/CMakeLists.txt and specify a 5.12+ Qt Kit to be used
  2. Build the project as usual (by pressing the build icon for instance)
  3. Open pyside-setup/sources/pyside2/CMakeLists.txt and specify the same 5.12+ Qt Kit
  4. Go to the projects tab, and under the Build / CMake section find the Shiboken2_DIR setting. You have to specify the path to the folder where the Shiboken CMake package was installed when you compiled Shiboken from the terminal·
  5. An example path under macOS is /Users/user/Dev/pyside2-setup/pyside_install/py3.6-qt5.12.1-64bit-debug/lib/cmake/Shiboken2-2.0.0. The path has to be adjusted depending on the user folder name, the version of python and qt, etc
  6. (Optional) On MacOS you also have to set the ALTERNATIVE_QT_INCLUDE_DIR setting to the Qt kit include path (e.g. /Users/user/Dev/qt511_source/include)
  7. Apply the CMake configuration changes (by pressing the button), and you should be able to build PySide

Now you can use the project explorer to look through the source cpp files, python files, use the locator feature to open files and file classes / methods, and other features that Qt Creator provides.

Troubleshooting / Known Issues

  • Qt 5.9 does not work with OpenSSL 1.1
    • When doing a custom Qt build (some unspecified versions for now), It is necessary to have an OpenSSL version of 1.0.x, since there are compatibility issues with newer versions of OpenSSL (see details)
  • PySide2 looks at the system installation if the local Qt version does not have a required module
    • The only workaround is to uninstall any module from the system, then PySide2 can look at only the Qt path currently being use.
  • Qt packages that directly link to OpenSSL (as opposed to runtime discovery) are not currently supported.
  • Make sure that the Python environment location where the PySide2 package will be installed is writable (otherwise you might get various permission denied errors). The install location can be found with 99% probability by running:
python -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())"
  • Building failing because graphviz wasn't found. If you're using pyenv and installed it using pip, try to install it using your package manager:
    dnf install graphviz.x86_64 #Fedora