Make sure only one PyQt window is shown

How do I switch between windows in PyQt5?

Here the Ui_Dialog2() represents that your are creating an object for new window (in your case creating object for Window1 for switch MainWindow to Window1 ). So when you click the next button this function is called so an object is created for the next window and the window will be opened. It’s still open next window.
 

How can I switch to another screen without opening a new window in PyQt5?

Create a main_UI with this structure: QMainWindow > QFrame (centralWidget) > QLayout > another_q_frame (this frame will contain both of your main pages) Now create 2 other QWidget (lets call them screen_1 & screen_2 ) windows containing one button each (this button would be used to switch between the screens)
 

How do I open another window in PyQt?

Creating a new window. In Qt any widget without a parent is a window. This means, to show a new window you just need to create a new instance of a widget. This can be any widget type (technically any subclass of QWidget ) including another QMainWindow if you prefer.