You might try to put a "self." in front of your Form object name:

Qt Code: 
  1. self.FT = FormTwo()
  2. self.FT.show()
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If you don't put it, garbage collection will remove that object as soon as setupUi method finishes. So the window will disappear.

But if you put a self there, object is kept in the memory so it won't disappear.