Note to self: always work with instances!

Thanks for all the help, Harsh.

For a deeper example, check this. Hope that helps clear your instance issue

from PyQt4.QtGui import QWidget, QPushButton, QHBoxLayout, QApplication
from PyQt4.QtCore import SIGNAL, SLOT
import sys

if __name__==’__main__’:

app = QApplication(sys.argv)
window = QWidget()
button = QPushButton(“Hello”)
layout = QHBoxLayout(window)
layout.addWidget(button)

def toggler():
if button.text() == “Hello”:
button.setText(“PyQt”)
else:
button.setText(“Hello”)

button.connect(button, SIGNAL(“clicked()”), toggler)

window.show()

app.exec_()

But I can’t make it work without the toggler() function explicitly referring to the button instance. I wanted to make it so the toggler function was passed the name of the instance by the signal.

I tried:
def toggler(x):
if x.text() == “Hello”:
x.setText(“PyQt”)
else:
x.setText(“Hello”)

button.connect(button, SIGNAL(“clicked()”), toggler(button))

I don’t understand why I can’t do this, and what I would have to do differently to make it work.

Sorry for flooding your comments recently, but hey at least you know your blog is teaching someone PyQt

Trying to take on board your advice, I came up with this:
from PyQt4.QtGui import QWidget, QPushButton, QHBoxLayout, QApplication
from PyQt4.QtCore import SIGNAL, SLOT
import sys

if __name__==’__main__’:

app = QApplication(sys.argv)

window = QWidget()
window.setWindowTitle(“Layouts 1″)
button = QPushButton(“Hello”)
layout = QHBoxLayout(window)

class Toggle(QPushButton):

def toggleText(self):
if button.text() == “Hello”:
button.setText(“PyQt”)
else:
button.setText(“Hello”)

layout.addWidget(button)
button.connect(button, SIGNAL(“clicked()”),\
button, SLOT(“toggleText()”))
window.show()

app.exec_()
The program runs with the error ‘No such slot QPushButton::toggleText()’.
Have I extended the class correctly? Do I need to define an __init__ for my class? Sorry for coming back for more help, it’s quite baffling trying to get my head around the documentation.

QAbstractButton.text() returns the QString text. Note that all properties of a class available in Qt can be got via property() and set via setProperty() [No 'get' business, like in Java]

2nd point is right. Registered slots of a class have a ‘signature’, (as in, “clicked()”, etc.), so you can’t push in functions into them to execute. Try the same approach by extending the class QPushButton and adding in a new method inside, instead of using an external function. This way you’d also learn how to extend/improve base Qt classes for your needs, as is the philosophy

I tried the following:
from PyQt4.QtGui import QWidget, QPushButton, QHBoxLayout, QApplication
from PyQt4.QtCore import SIGNAL, SLOT
import sys

if __name__==’__main__’:

app = QApplication(sys.argv)

window = QWidget()
window.setWindowTitle(“Layouts Ex. 1″)
button = QPushButton(“Hello”)
layout = QHBoxLayout(window)

def toggle():
if button["text"] == “Hello”:
return “PyQt”
else:
return “Hello”

layout.addWidget(button)
button.connect(button, SIGNAL(“clicked()”),\
button, SLOT(“setText(toggle())”))
window.show()

app.exec_()

Obviously it doesn’t work, for one or both of these reasons:
- button["text"] doesn’t return the text of the button (it was a complete guess as I couldn’t figure out where to find this info in the docs)
- maybe you can’t call a function in a slot like I tried to do with toggle()

Can you give me a pointer?

-Blahah

p.s. nice tutorial thanks, PyQt and python really starting to make sense after reading through your articles.

But anyways, that line isn’t needed in interpreter mode.

File “”, line 1
if __name__==’__main__’:
^
SyntaxError: invalid syntax