Pass extra arguments to PyQt slot without losing default signal arguments

Question

A PyQt button event can be connected in the normal way to a function so that the function receives the default signal arguments (in this case the button checked state):

def connections(self):
    my_button.clicked.connect(self.on_button)

def on_button(self, checked):
    print checked   # prints "True"

Or, the default signal arguments can be overridden using lambda:

def connections(self):
    my_button.clicked.connect(lambda: self.on_button('hi'))

def on_button(self, message):
    print message   # prints "hi"

Is there a nice way to keep both signal arguments so it can be directly received by a function like below?

def on_button(self, checked, message):
    print checked, message   # prints "True, hi"

You can subclass the button and create a new signal which will emit the state of a button and a message. — SnoozeTime, Jun 29 '16 at 04:31
[Eli Bendersky](https://eli.thegreenplace.net) posted [an article about this](https://eli.thegreenplace.net/2011/04/25/passing-extra-arguments-to-pyqt-slot) in 2011. — delrocco, Nov 09 '17 at 18:11

score 30 · Accepted Answer · edited Jun 12 '18 at 12:41

30

Your lambda could take an argument:

def connections(self):
    my_button.clicked.connect(lambda checked: self.on_button(checked, 'hi'))

def on_button(self, checked, message):
    print checked, message   # prints "True, hi"

Or you could use functools.partial:

# imports the functools module
import functools 

def connections(self):
    my_button.clicked.connect(functools.partial(self.on_button, 'hi'))

def on_button(self, message, checked):
    print checked, message   # prints "True, hi"

edited Jun 12 '18 at 12:41

Aditya Gupta

29
4

answered Jun 29 '16 at 12:42

The Compiler

11,126
4
40
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This answer never gets old. It keeps saving me. Thanks! – alete Jan 21 '19 at 17:42

Pass extra arguments to PyQt slot without losing default signal arguments

1 Answers1