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

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

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.

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!

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

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.

FIX: ensure that qt5agg and qt5cairo backends actually use qt5

runtime: Import PyQt5 before matplotlib to work around a bug

Obrigado!

runtime: Import PyQt5 before matplotlib to work around a bug

Navigation Menu

Repository navigation

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

Bug summary

Code for reproduction

Actual outcome

Expected outcome

Additional information

Operating system

Matplotlib Version

Matplotlib Backend

Python version

Installation

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

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

Description

Bug summary

Code for reproduction

Actual outcome

Expected outcome

Additional information

Operating system

Matplotlib Version

Matplotlib Backend

Python version

Installation

Activity

QuLogic commented on Dec 18, 2021

MusYi commented on Dec 18, 2021

QuLogic commented on Dec 19, 2021

tacaswell commented on Dec 19, 2021

weversonmachado commented on Jun 23, 2022

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions