My_Practice_:_Porting_python_scripts_to_PySide2

I wrote down my PySide2 porting notes and hopefully it's helpful for others who need to port PySide2.

Contents:

1. Handle both PySide and PySide2
2. Shiboken
3. QHBoxLayout QVBoxLayout
4. QHeaderView
5. QApplication.palette()

Handle both PySide and PySide2

Background: Qt5 add a new module QtWidgets. Compared with Qt4, Qt5 moved some classes to QtWidgets module instead of QtGui. For example, Qt4: QtGui.QWidget(). But it should be QtWidgets.QWidget() in Qt5.
Tricky part: some classes are still in QtGui. So we can't replace all QtGui with QtWidgets simply.

Solution: to both test Qt4 and Qt5 in the transition stage, I'm trying to remove module name from python scripts. The fixed code will be available for both Pyside(Qt4) and PySide2(Qt5).
After the change, you could use QWidget() instead of QtGui.QWidget().

try:
    from PySide import QtGui, QtCore
    from PySide.QtGui import *
    from PySide.QtCore import *
except ImportError:
    from PySide2 import QtGui, QtCore, QtWidgets
    from PySide2.QtGui import *
    from PySide2.QtCore import *
    from PySide2.QtWidgets import *

If you don't want to strip “QtGui” prefix, below is another solution:

try:
    from PySide import QtGui, QtCore
    import PySide.QtGui as QtWidgets
except ImportError:
    from PySide2 import QtGui, QtCore, QtWidgets

And the following code will work for both PySide and PySide2

QtWidgets.QLabel()
QtGui.QIcon()

Shiboken

It doesn't work if I import shiboken2 (windows). It complained that ImportError: dynamic module does not define init function (initeshiboken2).
Logged issue: https://github.com/PySide/pyside2/issues/61

Workaround: Please rename shiboken2.pyd to shiboken.pyd. import shiboken as before (Qt4 and PySide)

QHBoxLayout QVBoxLayout

Background:
Qt4 (PySide): QLayout::setAlignment(Qt::Alignment alignment)
http://doc.qt.io/qt-4.8/qlayout.html#setAlignment-2
Qt5 (PySide2): removed the above method
http://doc.qt.io/qt-5/qlayout.html#setAlignment
To upgrade to PySIde2, we have to make the following changes for
QHBoxLayout::setAlignment(Qt::Alignment alignment)
QVBoxLayout::setAlignment(Qt::Alignment alignment)

Qt4 (PySide):

layout = QHBoxLayout()
layout.setAlignment(Qt.AlignLeft)

Qt5(PySide2) : --solution

layout = QHBoxLayout()
QLayoutItem.setAlignment(layout, Qt.AlignLeft)

QHeaderView

Qt4 (PySide): http://doc.qt.io/qt-4.8/qheaderview.html

void    setResizeMode(ResizeMode mode);
void    setResizeMode(int logicalIndex, ResizeMode mode);

Qt5(PySide2) : http://doc.qt.io/qt-5/qheaderview.html

void    setSectionResizeMode(ResizeMode mode);
void    setSectionResizeMode(int logicalIndex, ResizeMode mode);

Solution:

pysideVersion = '-1'
try:
    import PySide
    pysideVersion = PySide.__version__
except ImportError:
    import PySide2
    pysideVersion = PySide2.__version__
if pysideVersion == '1.2.0':
    treeUI.header().setResizeMode(QHeaderView.Fixed)
    treeUI.header().setResizeMode(TREE_COLUMN_NAME, QHeaderView.Interactive)
    treeUI.header().setResizeMode(TREE_COLUMN_WEIGHT, QHeaderView.Stretch)
else:
    treeUI.header().setSectionResizeMode(QHeaderView.Fixed)
    treeUI.header().setSectionResizeMode(TREE_COLUMN_NAME, QHeaderView.Interactive)
    treeUI.header().setSectionResizeMode(TREE_COLUMN_WEIGHT, QHeaderView.Stretch)

QApplication.palette()

Background:
Qt4:
QPalette QApplication::palette()
http://doc.qt.io/qt-4.8/qapplication.html#palette

Qt5:
QPalette QGuiApplication::palette()
http://doc.qt.io/qt-5/qguiapplication.html#palette

Solution:
PySide(Qt4): palette = QApplication.palette()
PySide2 (Qt5): palette = QGuiApplication.palette()

Another workaround:

palette = self.palette()  # self is widget
# as you could also find palette() within QWidget class http://doc.qt.io/qt-5/qwidget.html   
# it works for both Qt4 and Qt5.