[Bug]: Working with PyQt5, the different import order will make different result. #21998

MusYi · 2021-12-18T05:21:15Z

Bug summary

Working with PyQt5, the different import order will make different result.

If import PyQt5 before import matplotlib, the program will run normally.
If import PyQt5 after import matplotlib, the program will riase TypeError at the method of QLayout.addWidget.

Code for reproduction

import sys

# program run correctly, if import PyQt5 here before import matplotlib
# from PyQt5.QtWidgets import QApplication, QVBoxLayout, QWidget 
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
# program will raise TypeError, if import import PyQt5 after import matplotlib
from PyQt5.QtWidgets import QApplication, QVBoxLayout, QWidget

if __name__ == "__main__":
    app = QApplication(sys.argv)
    # init figure
    fig = Figure()
    fig_canvas = FigureCanvas(fig)
    # init widget
    layout = QVBoxLayout()
    layout.addWidget(fig_canvas) # TypeError here, if import PyQt5 after import matlpotlib
    win = QWidget()
    win.setLayout(layout)
    # run
    win.show()
    sys.exit(app.exec())

Actual outcome

TypeError
addWidget(self, QWidget, stretch: int = 0, alignment: Union[Qt.Alignment, Qt.AlignmentFlag] = Qt.Alignment()): argument 1 has unexpected type 'FigureCanvasQTAgg'
  File "E:\CODE\Python\testroom.py", line 17, in <module>
    layout.addWidget(fig_canvas)

Expected outcome

expect no TypeError

Additional information

This Bug will not happen at the version v3.4.x of matplotlib.

Operating system

Windows

Matplotlib Version

3.5.1

Matplotlib Backend

QtAgg

Python version

Python 3.8.10

Installation

pip

The text was updated successfully, but these errors were encountered:

QuLogic · 2021-12-18T05:36:55Z

Both ways work fine for me; are you certain that Matplotlib loaded PyQt5 and not PySide2?

See this explanation, but the safest way to guarantee that Matplotlib loads the intended Qt wrapper is to import it first.

MusYi · 2021-12-18T12:38:02Z

Thanks, I got it.

I tried it in a new python environment which just install matplotlib and pyqt5, the program will run correctlly.

So I checked the python pip environment which cause the TypeError, it contains both pyqt5 and pyside6.

At that time the matplotlib automatically import pyside6, which will conflict with the later imported pyqt5 and generate an error.

Thanks again!

QuLogic · 2021-12-19T01:04:50Z

Ah yes, this would have broken in 3.5, because it added support for both Python wrappers of Qt6.

tacaswell · 2021-12-19T01:27:00Z

I am going to re-open this, even though you can work around this by changing the import order, we should not have that sort of brittleness. I'm working on a PR to fix this.

Because the code in qt_compat tries qt6 bindings first, backend_qt supports both Qt5 and Qt6, and the qt5 named backends are shims to the generic Qt backend, if you imported matplotlib.backends.backend_qt5agg, matplotlib.backends.backend_qt5cairo, or matplotlib.backends.backend_qt5, and 1. had PyQt6 or pyside6 installed 2. had not previously imported a Qt5 binding Then you will end up with a backend that (by name) claims to be Qt5, but will be using Qt6 bindings. If you then subsequently import a Qt6 binding and try to embed the canvas it will fail (due to being Qt6 objects not Qt5 objects!). closes matplotlib#21998

Because the code in qt_compat tries qt6 bindings first, backend_qt supports both Qt5 and Qt6, and the qt5 named backends are shims to the generic Qt backend, if you imported matplotlib.backends.backend_qt5agg, matplotlib.backends.backend_qt5cairo, or matplotlib.backends.backend_qt5, and 1. had PyQt6 or pyside6 installed 2. had not previously imported a Qt5 binding Then you will end up with a backend that (by name) claims to be Qt5, but will be using Qt6 bindings. If you then subsequently import a Qt6 binding and try to embed the canvas it will fail (due to being Qt6 objects not Qt5 objects!). closes matplotlib#21998 Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Because the code in qt_compat tries qt6 bindings first, backend_qt supports both Qt5 and Qt6, and the qt5 named backends are shims to the generic Qt backend, if you imported matplotlib.backends.backend_qt5agg, matplotlib.backends.backend_qt5cairo, or matplotlib.backends.backend_qt5, and 1. had PyQt6 or pyside6 installed 2. had not previously imported a Qt5 binding Then you will end up with a backend that (by name) claims to be Qt5, but will be using Qt6 bindings. If you then subsequently import a Qt6 binding and try to embed the canvas it will fail (due to being Qt6 objects not Qt5 objects!). Additional changes to qt_compat that only matters if 1. rcparams['backend'] is set to qt5agg or qt5agg 2. QT_API env is not set 3. the user directly import matplotlib.backends.qt_compat This will likely only affect users who are using Matplotlib as an qt-shim implementation. closes matplotlib#21998 Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

This works around matplotlib/matplotlib#21998 by importing PyQt5 before matplotlib. The bug was introduced in matplotlib 3.5 and fixed in 3.5.2, but Ubuntu 22.04 ships with 3.5.1. Signed-off-by: Clayton Smith <argilo@gmail.com>

This works around matplotlib/matplotlib#21998 by importing PyQt5 before matplotlib. The bug was introduced in matplotlib 3.5 and fixed in 3.5.2, but Ubuntu 22.04 ships with 3.5.1. Signed-off-by: Clayton Smith <argilo@gmail.com> (cherry picked from commit 76bd672) Signed-off-by: Jeff Long <willcode4@gmail.com>

weversonmachado · 2022-06-23T14:34:55Z

Obrigado!

This works around matplotlib/matplotlib#21998 by importing PyQt5 before matplotlib. The bug was introduced in matplotlib 3.5 and fixed in 3.5.2, but Ubuntu 22.04 ships with 3.5.1. Signed-off-by: Clayton Smith <argilo@gmail.com>

MusYi changed the title ~~[Bug]:~~ [Bug]: Working with PyQt5, the different import order will make different result. Dec 18, 2021

MusYi closed this as completed Dec 18, 2021

tacaswell reopened this Dec 19, 2021

tacaswell added this to the v3.5.2 milestone Dec 19, 2021

tacaswell mentioned this issue Dec 19, 2021

Further defer backend selection #22005

Merged

6 tasks

QuLogic closed this as completed in 2bc0c1c Mar 3, 2022

argilo mentioned this issue May 15, 2022

gr-perf-monitorx fails to run on Ubuntu 22.04 gnuradio/gnuradio#5848

Closed

argilo mentioned this issue May 15, 2022

Import PyQt5 before matplotlib to work around a bug gnuradio/gnuradio#5849

Merged

6 tasks

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[Bug]: Working with PyQt5, the different import order will make different result. #21998

[Bug]: Working with PyQt5, the different import order will make different result. #21998

MusYi commented Dec 18, 2021 •

edited

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QuLogic commented Dec 18, 2021

MusYi commented Dec 18, 2021

QuLogic commented Dec 19, 2021

tacaswell commented Dec 19, 2021

weversonmachado commented Jun 23, 2022

[Bug]: Working with PyQt5, the different import order will make different result. #21998

[Bug]: Working with PyQt5, the different import order will make different result. #21998

Comments

MusYi commented Dec 18, 2021 • edited Loading

Bug summary

Code for reproduction

Actual outcome

Expected outcome

Additional information

Operating system

Matplotlib Version

Matplotlib Backend

Python version

Installation

QuLogic commented Dec 18, 2021

MusYi commented Dec 18, 2021

QuLogic commented Dec 19, 2021

tacaswell commented Dec 19, 2021

weversonmachado commented Jun 23, 2022

MusYi commented Dec 18, 2021 •

edited

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