Okay, I think I kinda got it - I imported the class of the second form. This is somewhat the codes (but I changed the names of the classes mostly)

form1.py
Qt Code: 
  1. from PyQt4.QtGui import QMainWindow
  2. from PyQt4.QtCore import pyqtSignature
  3.  
  4. from Ui_form1 import Ui_MainWindow
  5.  
  6. from ui.form2 import FormTwo
  7.  
  8. class FormOne(QMainWindow, Ui_MainWindow):
  9.     """
  10.     Class documentation goes here.
  11.     """
  12.     def __init__(self, parent = None):
  13.         """
  14.         Constructor
  15.         """
  16.         QMainWindow.__init__(self, parent)
  17.         self.setupUi(self)
  18.  
  19.     @pyqtSignature("")
  20.     def on_button_released(self):
  21.         """
  22.         Slot documentation goes here.
  23.         """
  24.         FT = FormTwo()
  25.         FT.show()
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form2.py
Qt Code: 
  1. from PyQt4.QtGui import QDialog
  2. from PyQt4.QtCore import pyqtSignature
  3.  
  4. from Ui_form2 import Ui_Dialog
  5.  
  6. class FormTwo(QDialog, Ui_Dialog):
  7.     """
  8.     Class documentation goes here.
  9.     """
  10.     def __init__(self, parent = None):
  11.         """
  12.         Constructor
  13.         """
  14.         QDialog.__init__(self, parent)
  15.         self.setupUi(self)
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__init__.py
Qt Code: 
  1. from PyQt4 import QtCore, QtGui
  2. from ui.form1 import FormOne
  3.  
  4. if __name__ == "__main__":
  5.     import sys
  6.     app = QtGui.QApplication(sys.argv)
  7.     ui = FormOne()
  8.     ui.show()
  9.     sys.exit(app.exec_())
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There is a new problem though that the 2nd form doesn't stay at all and closes immediately after I click the button on the first form. Would it be alright to ask how to correct and solve this?