Lambda default value with Pyside6 events

Question

I'm porting an application from: python 3.8.5 / PyQt5, to : python 3.10.0 / PySide6

This code adds multiple QAction in a context menu and worked with python 3.8.5 / PyQt5:

for filepath in filepaths:
    action = QtGui.QAction(QtGui.QIcon('icon.png'), filepath, self)
    action.triggered.connect(lambda checked, path=filepath: self.open_file(path))
    menu.addAction(action)

But with python 3.10.0 / PySide6, I get this error when I click on the QAction :

menu.<locals>.<lambda>() missing 1 required positional argument: 'checked'

I'm not sure if it comes from the python upgrade or the PyQt5 => PySide6 change ?

Any workaround to keep a copy of the filepath value in the lambda ?

Answer 1

The problem comes from PySide6 (may be already PySide2) which does some argument analysis and don't permit lambda with default values.

Solution is to use functools.partial :

from functools import partial

class Example:

    def fill_menu(self, filepaths):

        for filepath in filepaths:
            action = QtGui.QAction(QtGui.QIcon('icon.png'), filepath, self)
            action.triggered.connect(partial(self.open_file, path))
            menu.addAction(action)

    def open_file(self, path):
        print(path)