How can I change the properties of an object when it's created in another file?

Check this example:
It's a simple form with a label and a button, when you click on the button the label must change to something else. To keep my code readable I want the GUI-creation in another file:

This is the mainfile:
Code:
import wx
import gui

class TestApp(wx.App):
    def OnInit(self):
        self.main = gui.create(None)
        self.main.Show()
        self.SetTopWindow(self.main)
        return True

def main():
    application = TestApp(0)
    application.MainLoop()

if __name__ == '__main__':
    main()

def OnButton1Click(event):
    gui.Frame1.Label1.Label = 'zever'
And the GUI-file
Code:
import wx
import main

def create(parent):
    return Frame1(parent)

[wxID_FRAME1, wxID_FRAME1BUTTON1, wxID_FRAME1LABEL1, wxID_FRAME1PANEL1, 
] = [wx.NewId() for _init_ctrls in range(4)]

class Frame1(wx.Frame):
    def _init_ctrls(self, prnt):
        # generated method, don't edit
        wx.Frame.__init__(self, id=wxID_FRAME1, name='', parent=prnt,
              pos=wx.Point(239, 326), size=wx.Size(414, 266),
              style=wx.DEFAULT_FRAME_STYLE, title='Frame1')
        self.SetClientSize(wx.Size(406, 239))

        self.panel1 = wx.Panel(id=wxID_FRAME1PANEL1, name='panel1', parent=self,
              pos=wx.Point(0, 0), size=wx.Size(406, 239),
              style=wx.TAB_TRAVERSAL)

        self.Label1 = wx.StaticText(id=wxID_FRAME1LABEL1, label='Label1',
              name='Label1', parent=self.panel1, pos=wx.Point(152, 56),
              size=wx.Size(31, 13), style=0)

        self.button1 = wx.Button(id=wxID_FRAME1BUTTON1, label='button1',
              name='button1', parent=self.panel1, pos=wx.Point(136, 104),
              size=wx.Size(75, 23), style=0)
        self.button1.Bind(wx.EVT_BUTTON, main.OnButton1Click,
              id=wxID_FRAME1BUTTON1)

    def __init__(self, parent):
        self._init_ctrls(parent)
I can click the button and the code (which is in the mainfile) is executed, but I cannot find how to change the label itself. In this example I get the error "AttributeError: type object 'Frame1' has no attribute 'Label1'. What's the right syntax for this? Keeping this all in one file, there's no problem, but I really want it to be splitted