python - In PyQT how to open a child window that has access to the parent's attributes? -

i have engine module contains several helper methods , attributes:

engine.py

class world:     def __init__(self):         # stuff      def foo(a, b):         c = + b # trivial example         return c 

then have main.py incorporates ui files (created in qtdesigner , converted .py using script have):

main.py

from pyqt4 import qtgui import design1 import design2 import engine  class mainwindow(qtgui.qmainwindow, design1.ui_mainwindow):     def __init__(self, parent=none):         super(mainwindow, self).__init__(parent)         self.setupui(self)         self.world = engine.world()          self.new_window_button.clicked.connect(self.open_new_window)      def open_new_window(self):         self.window_to_open = childwindow(self)         self.window_to_open.show()  class childwindow(qtgui.qmainwindow, design2.ui_mainwindow):     def __init__(self, parent):         super(childwindow, self).__init__(parent)         self.setupui(self)         print(self.world.foo(1, 2)) # trivial example  def main():     app = qtgui.qapplication(sys.argv)     window = mainwindow()     window.show()     app.exec() 

if take out print line, childwindow opens fine. in error:

attributeerror: 'childwindow' object has no attribute 'world'

i know i'm doing silly can't figure out.

edited main.py

from pyqt4 import qtgui import design1 import design2 import engine  class mainwindow(qtgui.qmainwindow, design1.ui_mainwindow):     def __init__(self, parent=none):         super(mainwindow, self).__init__(parent)         self.setupui(self)         self.world = engine.world()          self.new_window_button.clicked.connect(self.open_new_window)      def open_new_window(self):         self.window_to_open = childwindow(self)         self.window_to_open.show()  class childwindow(qtgui.qmainwindow, design2.ui_mainwindow):     def __init__(self, parent):         super(childwindow, self).__init__(parent)         self.setupui(self)         print(self.parent().world.foo(1, 2)) # trivial example  def main():     app = qtgui.qapplication(sys.argv)     window = mainwindow()     window.show()     app.exec() 

i error:

typeerror: foo() takes 2 positional arguments 3 given

the childwindow class not have attribute world, can access through the parent() function, returns parent since have used following statement: self.window_to_open = childwindow (self)

you must change

self.world.foo(1, 2) 

to

self.parent().world.foo(1, 2) 

your method must declared static since not use self parameter.

class world:     def __init__(self):         # stuff      @staticmethod     def foo(a, b):         c = + b # trivial example         return c 

or

def foo(self, a, b):     c = + b # trivial example     return c