Can't add widget from event call - qt

Question

I want to add a button during a event, but for some reason it doesn't work.
If i run this code, the TempFunc function will run during creation and a button will be created.
from PySide.QtGui import *
from PySide.QtCore import *
import sys
import math
class Example(QWidget):
def __init__(self, val):
super(Example,self).__init__()
self.scrollAreaConstraint = QLabel()
self.scrollAreaConstraint.setFixedSize(QSize(400,400))
self.scroll = QScrollArea()
self.scroll.setWidget(self.scrollAreaConstraint)
self.scroll.setWidgetResizable(True)
layout = QVBoxLayout(self)
layout.addWidget(self.scroll)
self.CountSlider = QSlider()
self.CountSlider.setOrientation(Qt.Orientation(1))
layout.addWidget(self.CountSlider)
self.TempFunc() #THIS WILL CREATE THE BUTTON!!
def TempFunc(self):
print "SLIDER PRESSED!!! NOW I WILL ADD A BUTTON"
QPushButton(self.scrollAreaConstraint)
if __name__ == '__main__':
import sys
app = QApplication(sys.argv)
window = Example(25)
window.setGeometry(500, 500, 500, 400)
window.show()
sys.exit(app.exec_())
However running this, pressing the slider will cause the same TempFunc function to run, but the button is not created.
from PySide.QtGui import *
from PySide.QtCore import *
import sys
import math
class Example(QWidget):
def __init__(self, val):
super(Example,self).__init__()
self.scrollAreaConstraint = QLabel()
self.scrollAreaConstraint.setFixedSize(QSize(400,400))
self.scroll = QScrollArea()
self.scroll.setWidget(self.scrollAreaConstraint)
self.scroll.setWidgetResizable(True)
layout = QVBoxLayout(self)
layout.addWidget(self.scroll)
self.CountSlider = QSlider()
self.CountSlider.setOrientation(Qt.Orientation(1))
layout.addWidget(self.CountSlider)
#self.TempFunc() #<----Disabled!!
self.CountSlider.sliderPressed.connect(self.TempFunc)
def TempFunc(self):
print "SLIDER PRESSED!!! NOW I WILL ADD A BUTTON"
QPushButton(self.scrollAreaConstraint)
if __name__ == '__main__':
import sys
app = QApplication(sys.argv)
window = Example(25)
window.setGeometry(500, 500, 500, 400)
window.show()
sys.exit(app.exec_())
Why is the button not created when not being called directly from the "init"?

Answer 1

The button is created, but then your code does nothing useful with it, which explains why it "doesn't work".
I'm guessing that, since you make scrollAreaConstraint the parent of these buttons, you are expecting them to appear inside the scroll-area. But scrollAreaConstraint is a QLabel, which cannot act as a container for other widgets.
So make scrollAreaConstraint a QWidget, give it a layout, and add the buttons to that layout:
self.scrollAreaConstraint = QWidget()
self.scrollAreaConstraint.setLayout(QVBoxLayout())
...
def TempFunc(self):
button = QPushButton(self.scrollAreaConstraint)
self.scrollAreaConstraint.layout().addWidget(button)

Answer 2

I eventually found that QT will set the .visible flag to false by default.
So just setting it to true makes the buttons visible in both cases.
Still not sure how and why it works when calling it from the init function as they are set to visible(false) aswell.