Qt for Python/GettingStarted/X11

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Revision as of 08:29, 3 September 2019 by Mariana Meireles (talk | contribs) (Requirements)

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  • GCC (Linux)
  • A Python interpreter (version Python 3.5+ or Python 2.7). One possibility is to to use a package from https://www.python.org/downloads/ , a system installed package with an appropriate version should work as well.
  • Qt 5.12
  • libclang 6.0 (for 5.12)
  • CMake from https://cmake.org/download/ (>= 3.1)
  • Git (>=2)
  • virtualenv (strongly recommended, but optional)
  • Python sphinx package for documentation (optional, pip install sphinx)
  • Depending on the distribution used, other dependencies may be required, such as:
    • libgl-dev
    • python-dev (or python3-dev)
    • python-distutils (or python3-distutils)
    • python-setuptools (or python3-setuptools)

Building from sources

Setting up CLANG

wget https://download.qt.io/development_releases/prebuilt/libclang/libclang-release_60-linux-Rhel7.2-gcc5.3-x86_64-clazy.7z
  • Extract the files, e.g.
7z x libclang-release_60-linux-Rhel7.2-gcc5.3-x86_64-clazy.7z                            
  • Export the installation path to the path you choosed to place the files
export CLANG_INSTALL_DIR=$PWD/libclang                                               

Getting PySide2

  • Clone the official repository:
git clone --recursive https://code.qt.io/pyside/pyside-setup
  • Check out the version you want to build, e.g. 5.12. Keep in mind that you must use the same version as your Qt installation.
cd pyside-setup && git checkout 5.12

Building PySide2

  • Check your Qt installation path, to specifically use that version of qmake to build PySide2:
which qmake
  • Build can take a few minutes, so it is recommended to use more than one CPU core (e.g. 8). Remember to replace the paths to your current qmake path:
python setup.py build --qmake=/path/to/qmake --build-tests --ignore-git --parallel=8

Installing PySide2

  • To install on the current directory, just run:
python setup.py install --qmake=/path/to/qmake  --openssl=/path/to/openssl --build-tests --ignore-git --parallel=8

Test installation

  • You can execute one of the examples to verify the process is properly working.
  • Remember to properly set the environment variables for Qt and PySide2.
python examples/widgets/widgets/tetrix.py


Development happens in the 5.12 and dev branches of the pyside-setup repository.

The top level repository has the following submodules:

  • sources/pyside2-tools: uic, rcc tools
  • examples/ (5.6 only, examples are no longer a submodule in 5.9+)

Contributions follow the standard process.

It is helpful to have debug binaries or symbols for Python available. Debug packages can be installed separately in some Linux distributions (e.g.: Ubuntu, the packages python3-dbg, libpython3-dbg provide a debug binary python3-dbg)

If your distribution does not include them, you can download python sources and compile it by yourself, e.g.

./configure --prefix=/where/to/install/python/path CFLAGS="-O0 -fno-inline -fno-omit-frame-pointer -g" LDFLAGS="-O0" CPPFLAGS="-O0" OPT="-O0 -g"
make install

It is also recommended to use a Virtual Environment for testing to be able to always start from a clean base and avoid issues with write permissions in installations.

A new virtual environment can be created as follows:

virtualenv -p /usr/bin/python3-dbg testenv                                          

Please take into consideration that the binary name might be different in your system, and that you can choose a different name for the environment instead of testenv.


  • Wrong RUNPATH / rpath

If you choose to build Python from sources in shared library configuration, it might be the case that the rpath is not set properly, which means that the built python binary might use the system python shared library, instead of the custom build shared library. You can patch the interpreter rpath values with a binary that PySide2 provides:

cd pyside-setup
./patchelf --set-rpath /path/to/your/local/python/lib /path/to/your/python/virtualenv/binary/python

And then you can proceed to re-install PySide2. (you can check if the patch worked with readelf -d /path/to/your/python/virtualenv/binary/python)

  • Missing libICU causes linking problems

From 5.9+ you can get a copy of libICU by specifying --standalone (but not including --iculib-url) as an argument to setup.py execution.

  • Recompile with -fPIC
This issue is usually encountered when using pyenv in a Linux distribution. It's necessary to reinstall python using pyenv with the following addendum:
env PYTHON_CFLAGS=-fPIC pyenv install -v 2.7.8