How to use Gtk.Button.clicked()? Wrong Number of arguments supplied

Question

I am trying to build a graphical interface with python in GTK+/Pygobject, but i am having some trouble. Mainly with events.

What do i need? To execute a simple function whenever a button is clicked. Sample code:

class Window(Gtk.Window):

def __init__(self):
    [...]
    button = Gtk.Button()
    icon = Gio.ThemedIcon(name="system-shutdown-symbolic")
    image = Gtk.Image.new_from_gicon(icon, Gtk.IconSize.BUTTON)
    button.add(image)
    button.clicked(self.on_button_clicked())
    hb.pack_end(button)
    [...]


def on_button_clicked(self):
    print("Hello World")

Traceback:

Traceback (most recent call last): File "main.py", line 7, in executa = igrafica.Window() File "[...]/igrafica.py", line 23, in init button.clicked(self.on_button_clicked()) TypeError: clicked() takes exactly 1 argument (2 given)

It seemed quite obvious what button.clicked() should do, but its traceback talks about wrong numbers of arguments, and i can't find out what the problem is from this documentation i found. What am i doing wrong?

PS: Is there any official not "too-much-hardcore-for-newbies" documentation?

Answer 1

It does seem obvious what the clicked signal should do, but you're misunderstanding the syntax for connecting a signal handler. Normally that would raise a more intuitive error, but in this case there's also a clicked() method on Gtk.Button that you are inadvertently calling. (That method is part of very old but not-yet-deprecated API, and fires a fake clicked signal.)

Do this:

button.connect('clicked', self.on_button_clicked)

(remember not to put () after self.on_button_clicked, as eduffy pointed out, because you're not calling the method, but passing it as a parameter to another method.)

Answer 2

 button.clicked(self.on_button_clicked())

you are calling on_button_clicked right here. remove the () to simply reference the method:

 button.clicked(self.on_button_clicked)