mottosso/qt5.py

Minimal Python 2 & 3 shim around PySide2 and PyQt5

Qt5.py enables you to write software that runs the same on both PySide2 and PyQt5.

See also

• Qt.py - Like Qt5.py, with added support for PySide and PyQt4.

Goals

Write once, run in any binding.

Qt5.py is the younger brother to Qt.py and provides extended support for features unique to Qt 5, such as QtQml, QtMultimedia and QtWebAssembly.

Goal	Description
Support co-existence	Qt5.py should not affect other bindings, not even Qt.py, running in the same interpreter session
Build for one, run with all	Code written with Qt5.py should run identically on both PySide2 and PyQt5
Explicit is better than implicit	Differences between bindings should be visible to you.

Install

Qt5.py is a single file and can be either copy/pasted into your project, downloaded as-is, cloned as-is or installed via pip.

# From PyPI
$ pip install Qt5.py

• Pro tip: The direct download and clone options refer to the latest commit of this project, which is typically beta. For the latest stable release, refer to any of the official releases
• Pro top: Qt5.py supports vendoring

Usage

Use Qt5.py as you would use PySide2.

import os
import sys
import tempfile

from Qt5 import QtGui, QtQml

f = tempfile.NamedTemporaryFile("w", delete=False)
f.write("""\
import QtQuick 2.4
import QtQuick.Controls 1.4

ApplicationWindow {
    title: "My App"
    width: 240
    height: 180
    visible: true

    Button {
        text: "Hello World"
        anchors.centerIn: parent
    }
}
""")
f.close()

app = QtGui.QGuiApplication(sys.argv)
engine = QtQml.QQmlApplicationEngine()
engine.load(f.name)
engine.quit.connect(app.quit)
app.exec_()
os.remove(f.name)

qt5.py's Issues

Create setup.py and register PyPI name

Without a setup.py the repository can't really be used as a dependency (I'm not sure if it is a good idea to encourage "copy-and-paste" usage :)

Outdated pacakge version on PyPI

The Qt5.py on PyPI is still in version 0.1.0, which is so old.
Will there be an automated publishment like Qt.py have ?

Qt5 import issue compared with Qt, PyQt or Pyside

the old Qt module can easily subsitute Pyside2
but when trying that with the new Qt5 it has to be done in a specific way.

it doesn't allow us to do this

from PySide2.QtWidgets import QApplication
from Qt.QtWidgets import QApplication
from Qt5.QtWidgets import QApplication  # errors

Traceback (most recent call last):
  File "<blender_console>", line 1, in <module>
ModuleNotFoundError: No module named 'Qt5.QtWidgets'; 'Qt5' is not a package

This is fine

import PySide2
import Qt
import Qt5

This is fine

from PySide2 import QtWidgets
from Qt import QtWidgets
from Qt5 import QtWidgets

QtCore.QVariant for PySide

QtCore.QVariant was missing in PySide, but the document mentioned that one could just use "QVariant" like:

signal = QtCore.Signal("QVariant")

This works for Python built-in types, but looks like not all custom types will be handled properly.

import sys
from PySide2 import QtWidgets, QtCore

QtCore.QVariant = "QVariant"


class Sheet(list):
    pass


class Thing(object):
    pass


class Application(QtWidgets.QApplication):

    variant = QtCore.Signal(QtCore.QVariant)

    def __init__(self):
        super(Application, self).__init__(sys.argv)

        window = QtWidgets.QWidget()
        button = QtWidgets.QPushButton("Emit")

        layout = QtWidgets.QVBoxLayout(window)
        layout.addWidget(button)

        button.clicked.connect(self.emit_variant)
        self.variant.connect(self.process)
        self.window = window

        window.show()

    def emit_variant(self):
        self.variant.emit(Sheet(["a", "b"]))
        self.variant.emit(Thing())

    def process(self, variant):
        print(type(variant), variant)


if __name__ == "__main__":
    app = Application()
    app.exec_()

Hit the Emit button and the result will be:

<class 'list'> ['a', 'b']
<class '__main__.Thing'> <__main__.Thing object at 0x000002204CEA1240>

Notice that although the instance of Thing stays the same, but the instance of Sheet has became just a list.

But if you change "QVariant" to object

QtCore.QVariant = object

Then:

<class '__main__.Sheet'> ['a', 'b']
<class '__main__.Thing'> <__main__.Thing object at 0x000001E0A0DC1240>

They both get preserved.

So maybe we should use object instead of "QVariant" to fill up this gap ?
And, anyone knows why it works in this way in PySide ?

QtCompat.loadUi for PyQt5

This was part of Qt.py but hasn't been ported over yet: https://github.com/mottosso/Qt.py/#compatibility

pyqtSignal and friends available on PyQt5

A current limitation of the way Qt5.py has been implemented is that, even though QtCore.Signal is consistent across both PySide2 and PyQt5, it doesn't successfully prohibit the use of pyqtSignal.