Why PYQT5 connecting multiple checkboxes does not work in a loop, but works by writing out everything manually

Question

I am working on PyQT5 and I have the following list.

self.config_cbs = [self.gui.cb_config_0, \
                   self.gui.cb_config_1, \
                   self.gui.cb_config_2, \
                   self.gui.cb_config_3, \
                   self.gui.cb_config_4, \
                   self.gui.cb_config_5, \
                   self.gui.cb_config_6, \
                   self.gui.cb_config_7, \
                   self.gui.cb_config_8, \
                   self.gui.cb_config_9, \
                   self.gui.cb_config_10, \
                   self.gui.cb_config_11]

I want to connect all checkboxes to the same function.

Does anyone know, why does this NOT work?

for i, cb in enumerate(self.config_cbs):
      cb.stateChanged.connect(lambda: self.config_cb_state_changed(i))

But this does work:

self.gui.cb_config_0.stateChanged.connect(lambda: self.config_cb_state_changed(0))
self.gui.cb_config_1.stateChanged.connect(lambda: self.config_cb_state_changed(1))
self.gui.cb_config_2.stateChanged.connect(lambda: self.config_cb_state_changed(2))
...

Aren't these two equivalent?

zigma12 · Accepted Answer · 2022-08-05T08:06:44.413

1

~~Solution 1~~

Can you try with this?

for i, cb in enumerate(self.config_cbs):
    cb.stateChanged.connect(lambda i=i: self.config_cb_state_changed(i))

Solution 2

If it still does not work, you can still alter your function config_cb_state_changed() and identify the checkbox which triggered the signal with self.sender() (I assume all the code is part of the same class).

...
for cb in self.config_cbs:
    cb.stateChanged.connect(self.config_cb_state_changed)
...

def config_cb_state_changed(state: bool):
    cb = self.sender()
    # If needed, you can find your index i
    i = self.config_cbs.index(cb)
    # And just to be sure...
    assert isinstance(cb, QCheckBox)
    assert cb.isChecked() == state

Solution 1 edited

for i, cb in enumerate(self.config_cbs):
    cb.stateChanged.connect(lambda state, i=i: self.config_cb_state_changed(i))

edited Aug 05 '22 at 08:06

answered Aug 05 '22 at 07:52

zigma12

181
1
7

The first solution did not work, the second did work, however I find it weird that I even have to do that.... Thank you anyway... – Jokubas11 Aug 05 '22 at 07:58
You did not mention the problem. I guess: whichever checkbox you click, you get `i=11` (the last added)? – zigma12 Aug 05 '22 at 08:00
See this (it refers to PyQt4 but the problem is the same): https://python.tutorialink.com/connecting-slots-and-signals-in-pyqt4-in-a-loop/ – zigma12 Aug 05 '22 at 08:02
yes, that is correct – Jokubas11 Aug 05 '22 at 08:11
Can you try the solution 1 I edited in my first message? – zigma12 Aug 05 '22 at 08:19

Why PYQT5 connecting multiple checkboxes does not work in a loop, but works by writing out everything manually

1 Answers1