How to pass arguments to functions by the click of button in PyQt?

Question

I want to pass the arguments to a function when I click the button. What should I add to this line button.connect(button, QtCore.SIGNAL('clicked()'), calluser(name)) so it will pass the value to the function:

def calluser(name):
    print name

def Qbutton():
    button = QtGui.QPushButton("button",widget)
    name = "user"
    button.setGeometry(100,100, 60, 35)
    button.connect(button, QtCore.SIGNAL('clicked()'), calluser(name))

One more thing, buttons will be generated using for loop; so name value will vary. So I want to attach each name with the button. I have done same thing in Pytk by using for loop and calling the argument base function when clicked.

you need to set the variable "name" somewhere.. where is that being set? — Tom Studee, Jul 21 '11 at 23:41
The lambda method works for me and maintains the Qt program structure: https://stackoverflow.com/a/53928495/7944058 — Casey, Jun 20 '19 at 20:50

score 115 · Answer 1 · answered Jul 23 '19 at 15:01

115

You can simply write

name = "user"
button.clicked.connect(lambda: calluser(name))

answered Jul 23 '19 at 15:01

ozcanyarimdunya

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Even More elegant! loved it! – NinjasAtWork Jul 31 '19 at 17:27
24

if the above does not work (for example inside a loop), do this: button.clicked.connect(lambda state, x=name: calluser(x)) – magamig Apr 22 '20 at 18:43
2

Your answer is exactly what I was looking for... Thank you so much! – SALMAANYEHIA Jul 13 '20 at 22:25
Perfect solution! – jaw12346 Aug 17 '21 at 19:52
@magamig why does the above not work inside a loop? – payala Dec 20 '21 at 21:46
each time signal will be assigned to same function, at the end of loop last item will be assigned to method. thats why it doesnt work inside loop, you should think different logic – ozcanyarimdunya Dec 20 '21 at 22:39

xeon · Answer 2 · 2017-07-24T12:23:07.847

40

I tried an efficient way of doing it and it worked out well for me. You can use the code:

from functools import partial

def calluser(name):
    print name

def Qbutton():
    button = QtGui.QPushButton("button",widget)
    name = "user"
    button.setGeometry(100,100, 60, 35)
    button.clicked.connect(partial(calluser,name))

edited Jul 24 '17 at 12:23

answered Mar 22 '17 at 07:14

xeon

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very elegant :D – NinjasAtWork Jul 31 '19 at 17:05
5

Has anyone actually tried this with multiple names before upvoting? Partial will freeze the name. I.e. once it is set to "user", there is no way you can change it via the GUI. – Julius Jul 19 '21 at 15:44

unutbu · Answer 3 · 2013-02-06T20:54:16.630

Usually GUIs are built using classes. By using bound methods as callbacks (see self.calluser below) you can "pass" information to the callback through self's attributes (e.g. self.name):

For example, using slightly modified code from this tutorial:

import sys
import PyQt4.QtCore as QtCore
import PyQt4.QtGui as QtGui

class QButton(QtGui.QWidget):
    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.button = QtGui.QPushButton('Button', self)
        self.name='me'
        self.button.clicked.connect(self.calluser)
    def calluser(self):
        print(self.name)

def demo_QButton():
    app = QtGui.QApplication(sys.argv)
    tb = QButton()
    tb.show()
    app.exec_()

if __name__=='__main__':
    demo_QButton()

Since the callback per se is always called with no additional arguments, when you need to pass distinct additional information to many callbacks, you need to make different callbacks for each button.

Since that can be laborious (if done manually), use a function factory instead. See below for an example. The function factory is a closure. It can be passed additional arguments, which the inner function can access when called:

class ButtonBlock(QtGui.QWidget):

    def __init__(self, *args):
        super(QtGui.QWidget, self).__init__()
        grid = QtGui.QGridLayout()
        names = ('One', 'Two', 'Three', 'Four', 'Five',
                 'Six', 'Seven', 'Eight', 'Nine', 'Ten')
        for i, name in enumerate(names):
            button = QtGui.QPushButton(name, self)
            button.clicked.connect(self.make_calluser(name))
            row, col = divmod(i, 5)
            grid.addWidget(button, row, col)
        self.setLayout(grid)

    def make_calluser(self, name):
        def calluser():
            print(name)
        return calluser

app = QtGui.QApplication(sys.argv)
tb = ButtonBlock()
tb.show()
app.exec_()

Thanks for the reply, but in my case the value of the name will change as the buttons will be generated by a for loop. So can I pass the values as arguments to the function? — uahmed, Jul 22 '11 at 13:55
+1; the calluser-Function can also access any methods or attributes via self.* This works, where lambda functions fail! — LuWi, Jul 29 '16 at 10:59
I guess it has something to do with scopes, but I'm not entierly sure. I was glad to get it working ;) — LuWi, Jan 18 '18 at 22:38

score 5 · Answer 4 · answered Dec 18 '13 at 12:24

Here is another way. --- PARTIAL -- I find this one most simple:

    widget = QWidget()
    widgetLayout = QVBoxLayout()

    for action in list:

        button = QPushButton("{action}".format(action=action['name']),self)
        button.clicked.connect(partial(self.action_selected,action=action['name']))
        widgetLayout.addWidget(button)

    widget.setLayout(widgetLayout)

def action_selected(self,action):
    print action

found on: http://tech-artists.org/forum/showthread.php?3118-PyQt-Maya-How-to-pass-arguments-to-a-function-when-connecting-it-to-PyQt-button

It doesn't seem to work if the input argument changes. E.g. `button.clicked.connect(partial(self.function, self.currentSelection))` if `self.currentSelection` is changed. Then you should set the argument inside the function via `self`, or create a nested function. — komodovaran_, Apr 25 '18 at 09:41

score 5 · Answer 5 · answered Aug 04 '16 at 21:00

In Python, class instances are callable. You can just use an instance of a class as a function. That class can contain whatever you want. (In some languages or frameworks, a callable object is called a functor or a function object.)

class CallUser:
    def __init__(self, name):
        self.name = name
    def __call__(self):
        print(self.name)

def Qbutton():
    button = QtGui.QPushButton("button",widget)
    name = "user"
    button.setGeometry(100,100, 60, 35)
    button.clicked.connect(CallUser(name))
    # Object of type CallUser will work as a function!

score 0 · Answer 6 · answered Apr 20 '16 at 07:29

The code shown below illustrates a method of associating data with generated buttons. For example, you could change the statement self.keydata[b] = key to store a tuple of data into self.keydata[b] for use when processing a button event later.

Note, in the following code, assets is a previously-defined dictionary containing titles for buttons. In the processButton(self) routine, self.sender() is equal to an entry in the class variable buttons[].

class Tab5(QtGui.QWidget):
    buttons, keydata = {}, {}
    def __init__(self, fileInfo, parent=None):
        super(Tab5, self).__init__(parent)
        layout = QtGui.QVBoxLayout()

        for key in sorted(assets):
            b = self.buttons[key] = QtGui.QPushButton(assets[key], self)
            b.clicked.connect(self.processButton)
            layout.addWidget(b)
            print 'b[key]=',b, ' b-text=',assets[key]
            self.keydata[b] = key

        layout.addStretch(1)
        self.setLayout(layout)

    def processButton(self):
         print 'sender=',self.sender(), ' s-text=',self.sender().text(), ' data[.]=', self.keydata[self.sender()] 
         pass

Output was like the following, where the first four lines printed during the for loop, and the last four printed when the four buttons were pressed in order.

b[key]= <PySide.QtGui.QPushButton object at 0x7f382f2ca830>  b-text= K1
b[key]= <PySide.QtGui.QPushButton object at 0x7f382f2ca908>  b-text= K2
b[key]= <PySide.QtGui.QPushButton object at 0x7f382f2ca950>  b-text= K3
b[key]= <PySide.QtGui.QPushButton object at 0x7f382f2ca998>  b-text= K4
sender= <PySide.QtGui.QPushButton object at 0x7f382f2ca830>  s-text= K1  data[.]= L1
sender= <PySide.QtGui.QPushButton object at 0x7f382f2ca908>  s-text= K2  data[.]= L2
sender= <PySide.QtGui.QPushButton object at 0x7f382f2ca950>  s-text= K3  data[.]= L3
sender= <PySide.QtGui.QPushButton object at 0x7f382f2ca998>  s-text= K4  data[.]= L4

score 0 · Answer 7 · answered Mar 08 '22 at 13:12

0

You can do with parameters as well,

button.cliked.connect(lambda self.change_value( "extra"))

the function

def change_value( extraVariable):
     print( extraVariable)

answered Mar 08 '22 at 13:12

MD SHAYON

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Isn't there a `c` and a `:` missing? Shouldn't it be: `button.clicked.connect(lambda: self.change_value( "extra"))` And I don't see anything new compared to @ozcanyarimdunya's answer from 2019. – theozh Jul 29 '22 at 14:59

How to pass arguments to functions by the click of button in PyQt?

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