How to Pass Extra Arguments to Qt Slots Using Lambda Functions or functools.partial?

Passing Extra Arguments through Connect

When connecting slots in Qt applications, there may be a need to pass additional arguments to the slot function. This can be done in two ways: using lambda functions or functools.partial.

Using Lambda Functions

Lambda functions allow you to pass extra arguments as keyword arguments when connecting a signal to a slot. The following is the general syntax:

connect(lambda param1, param2, ..., arg1=val1, arg2=value2, ... : fun(param1, param2,... , arg1, arg2, ....))

Where:

• param1, param2, ...: Parameters received by the signal
• arg1, arg2, ...: Extra parameters passed to the slot function

In your case, the code would be:

self.buttonGroup.buttonClicked['int'].connect(lambda i: self.input(i, "text"))

@pyqtSlot(int)
def input(self, button_or_id, DiffP):
    # Use the extra argument `DiffP` in the slot function
    ...

Using Functools.Partial

Functools.partial provides another method for passing extra arguments to slot functions. It creates a new function that is bound to the specified arguments. The general syntax is:

partial(fun, args1, arg2, ... )

Where:

• fun: Target slot function
• args1, arg2, ...: Extra arguments passed to the new function

Here's how you would use it in your code:

from functools import partial

...

self.buttonGroup.buttonClicked['int'].connect(partial(self.input, "text"))

@pyqtSlot(int)
def input(self, DiffP, button_or_id):
    # `DiffP` will be passed as the first argument to the slot function
    ...

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