CODEWITHSUNDEEP
pythonqt
Derrick Jones
Derrick Jones

Reputation: 11

QT disappearing second window

I am new to QT and have used QT 5 for programming in python. I have a main window but when I try to click a button for the second window, it shows but quickly disappears. Does anyone know how I can fix this issue?

def SecondWindow():
    qw = QWidget()
    qw.resize(800, 800)
    qw.move(300, 300)
    qw.show()

Upvotes: 1

Views: 282

Answers (1)

Kuba hasn't forgotten Monica
Kuba hasn't forgotten Monica

Reputation: 98435

Python is different than C++: in the latter, the code would work as desired, even if you'd leak the widget. Technically we wouldn't leak the widget since it's accessible from QApplication::topLevelWidgets.

In Python, there are no references to qw after SecondWindow finishes: it is a local variable. Thus the widget is destroyed immediately, since Python first uses reference counting for object lifetime management - and a garbage collector only to collect objects that form cycles, and that's not the case here.

The solution is to keep a reference to the widget you've created:

class MyClass(QObject):
  @pyqtSlot()
  def second_windowClick(self):
     self.SecondWindow()

  def SecondWindow(self):
     qw = QWidget()
     qw.resize(800, 800)
     qw.move(300, 300)
     qw.show()
     self.qw = qw

Upvotes: 2

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