Send Additional Variable During Pyqt Pushbutton Click

I'm new to Python and PyQt and this is my first application. Currently when a button is clicked, toggleLED() checks self.LedOn to decide whether to turn an LED on. class Screen(QWi

Solution 1:

You can use partial for that:

from functools import partial

btn1.clicked.connect(partial(self.toggleLED, 1))

This allows you to pass multiple arguments to a function.

Solution 2:

To pass multiple arguments to a function, you can use either functools.partial() or a lambda:

btn2.clicked.connect(lambda: selftoggleLED(2))

Read the discussion of both methods.

Solution 3:

Here is the solution that I always use for this job.

classScreen(QWidget):

    definitUI(self):

        btn1 = QPushButton('Off', self)
        btn1.setCheckable(True)
        btn1.LedOn= 0
        btn1.clicked.connect(selftoggleLED(1))

        btn2 = QPushButton('Off', self)
        btn2.setCheckable(True)
        btn2.LedOn= 0# I am adding these lines-----------------------# put all the btns in a list
        btns = [btn1, btn2]
        # connect each btn with the function and pass the same btnmap(lambda btn: btn.clicked.connect(lambda pressed: self.toggleLED(pressed, btn)), btns)


    deftoggleLED(self, pressed, clikedBtn):

        if pressed:
            clickedBtn.setText("On")
            # set other variables you needelse: 
            clickedBtn.setText("Off")
            # set other variables  

Solution 4:

class Screen(QWidget):

    def initUI(self):

        btn1 = QPushButton('Off', self)
        btn1.setCheckable(True)
        btn1.value = 1
        btn1.clicked.connect(selftoggleLED)

        btn2 = QPushButton('Off', self)
        btn2.setCheckable(True)
        btn2.value = 2
        btn2.clicked.connect(selftoggleLED)


    def toggleLED(self, pressed):

        source = self.sender()

        if pressed:
            source.setText('Off')
            self.serial.write(source.value)
            self.serial.write('L')
        else:           
            source.setText('On')
            self.serial.write(source.value)
            self.serial.write('H')

1. The checkable QPushButton will store the state, so you don't need btn.LedOn.
2. Use btn.value to store the btn number, so you don't need to send the extra arg.

Solution 5:

QPushButton does already have checked boolean property, so you don't need to create another one. There are two signals which button emits:

1. clicked when it's pressed
2. toggled when its state is changed

Both of them transfer parameter which indicates a button's state. But I think, the second is more appropriate because of its name.

So the toggleLED slot should looks like this:

def toggleLED(self, checked):
    source = self.sender()
    if checked:
        source.setText('Off')
        self.serial.write('L')
    else:           
        source.setText('On')
        self.serial.write('H')

Notice that only checkable buttons emit toggled signal, but you already set this property in your code:

definitUI(self):
    btn1 = QPushButton('Off', self)
    btn1.setCheckable(True)
    btn1.toggled.connect(self.toggleLED)

    btn2 = QPushButton('Off', self)
    btn2.setCheckable(True)
    btn2.toggled.connect(self.toggleLED)