wxPython and sharing objects between windows

Question

I've been working with python for a while now and am just starting to learn wxPython. After creating a few little programs, I'm having difficulty understanding how to create objects that can be shared between dialogs.

Here's some code as an example (apologies for the length - I've tried to trim):

import wx

class ExampleFrame(wx.Frame):
    """The main GUI"""
    def __init__(self, parent, id, title):
        wx.Frame.__init__(self, parent, id, title, size=(200,75))
        mainSizer = wx.BoxSizer(wx.VERTICAL)

        # Setup buttons
        buttonSizer = wx.BoxSizer(wx.HORIZONTAL)
        playerButton = wx.Button(self, wx.ID_ANY, "Player number", wx.DefaultPosition, wx.DefaultSize, 0)
        buttonSizer.Add(playerButton, 1, wx.ALL | wx.EXPAND, 0)
        nameButton = wx.Button(self, wx.ID_ANY, "Player name", wx.DefaultPosition, wx.DefaultSize, 0)
        buttonSizer.Add(nameButton, 1, wx.ALL | wx.EXPAND, 0)

        # Complete layout and add statusbar
        mainSizer.Add(buttonSizer, 1, wx.EXPAND, 5)
        self.SetSizer(mainSizer)
        self.Layout()

        # Deal with the events
        playerButton.Bind(wx.EVT_BUTTON, self.playerButtonEvent)
        nameButton.Bind(wx.EVT_BUTTON, self.nameButtonEvent)
        self.Show(True)
        return

    def playerButtonEvent(self, event):
        """Displays the number of game players"""
        playerDialog = PlayerDialogWindow(None, -1, "Player")
        playerDialogResult = playerDialog.ShowModal() 
        playerDialog.Destroy()
        return

    def nameButtonEvent(self, event):
        """Displays the names of game players"""
        nameDialog = NameDialogWindow(None, -1, "Name")
        nameDialogResult = nameDialog.ShowModal() 
        nameDialog.Destroy()
        return

class PlayerDialogWindow(wx.Dialog):
    """Displays the player number"""
    def __init__(self, parent, id, title):
        wx.Dialog.__init__(self, parent, id, title, size=(200,120))

        # Setup layout items
        self.SetAutoLayout(True)
        mainSizer = wx.BoxSizer(wx.VERTICAL)
        dialogPanel = wx.Panel(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize, wx.TAB_TRAVERSAL)
        dialogSizer = wx.BoxSizer(wx.VERTICAL)

        # Display player number
        playerNumber = "Player number is %i" % gamePlayer.number
        newLabel = wx.StaticText(dialogPanel, wx.ID_ANY, playerNumber, wx.DefaultPosition, wx.DefaultSize, 0)
        dialogSizer.Add(newLabel, 0, wx.ALL | wx.EXPAND, 5)

        # Setup buttons
        buttonSizer = wx.StdDialogButtonSizer()
        okButton = wx.Button(dialogPanel, wx.ID_OK)
        buttonSizer.AddButton(okButton)
        buttonSizer.Realize()
        dialogSizer.Add(buttonSizer, 1, wx.EXPAND, 5)

        # Complete layout
        dialogPanel.SetSizer(dialogSizer)
        dialogPanel.Layout()
        dialogSizer.Fit(dialogPanel)
        mainSizer.Add(dialogPanel, 1, wx.ALL | wx.EXPAND, 5)
        self.SetSizer(mainSizer)
        self.Layout()

        # Deal with the button events
        okButton.Bind(wx.EVT_BUTTON, self.okClick)
        return

    def okClick(self, event):
        """Deals with the user clicking the ok button"""
        self.EndModal(wx.ID_OK)
        return 

class NameDialogWindow(wx.Dialog):
    """Displays the player name"""
    def __init__(self, parent, id, title):
        wx.Dialog.__init__(self, parent, id, title, size=(200,120))

        # Setup layout items
        self.SetAutoLayout(True)
        mainSizer = wx.BoxSizer(wx.VERTICAL)
        dialogPanel = wx.Panel(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize, wx.TAB_TRAVERSAL)
        dialogSizer = wx.BoxSizer(wx.VERTICAL)

        # Display player number
        playerNumber = "Player name is %s" % gamePlayer.name
        newLabel = wx.StaticText(dialogPanel, wx.ID_ANY, playerNumber, wx.DefaultPosition, wx.DefaultSize, 0)
        dialogSizer.Add(newLabel, 0, wx.ALL | wx.EXPAND, 5)

        # Setup buttons
        buttonSizer = wx.StdDialogButtonSizer()
        okButton = wx.Button(dialogPanel, wx.ID_OK)
        buttonSizer.AddButton(okButton)
        buttonSizer.Realize()
        dialogSizer.Add(buttonSizer, 1, wx.EXPAND, 5)

        # Complete layout
        dialogPanel.SetSizer(dialogSizer)
        dialogPanel.Layout()
        dialogSizer.Fit(dialogPanel)
        mainSizer.Add(dialogPanel, 1, wx.ALL | wx.EXPAND, 5)
        self.SetSizer(mainSizer)
        self.Layout()

        # Deal with the button events
        okButton.Bind(wx.EVT_BUTTON, self.okClick)
        return

    def okClick(self, event):
        """Deals with the user clicking the ok button"""
        self.EndModal(wx.ID_OK)
        return 

class Player(object):
    """A game player"""
    def __init__(self, number, name):
        self.number = number
        self.name = name
        return

def main():
    # Start GUI
    global gamePlayer
    gamePlayer = Player(1, "John Smith")
    app = wx.App(redirect=False)
    frame = ExampleFrame(None, -1, "Example frame")
    frame.Show(True)
    app.MainLoop()
    return 0

if __name__ == '__main__':
    main()

So, I want both of the dialogs to access the gamePlayer object. At the moment, the only way I can think of doing it is to create the gamePlayer object as a global object, but these are normally frowned upon - is there a better way to do this?

There is a method of passing objects in event bindings in this question, but it doesn't feel quite right.

Is learning to implement the MVC pattern the way forward here?

Thanks.

Answer 1

A Model-View-Controller (MVC) framework allows you to access common data (Model) and display it in your GUI (Views) through a Controller. A good explanation is found here:

MVC Framework for wxPython

Basically, you avoid tangled messes by not allowing the model to talk to the views directly, but rather posting to a controller that it has made changes. The controller then updates the views appropriately. Likewise for updating the model from controls on you gui. This way the model and view code are independent, and they are tied together with the controller code that access the APIs of each.

Answer 2

You can pass a gamePlayer object to __init__ as another argument.

def __init__(self, parent, id, title, gamePlayer ):
    ...etc...

In the long run, this isn't ideal.

You should separate building an empty panel from loading that panel with data. The empty panel is one thing, populating it with data from the model is unrelated.

Populating a frame with data is where you must be given the gamePlayer object which will be used to update the various display widgets.

I'd suggest you look at the Document-View framework for guidance on this. http://docs.wxwidgets.org/stable/wx_docviewoverview.html#docviewoverview. Unfortunately, there aren't any good Python examples of this, so it can be confusing to convert from the C++ code to Python.

Ultimately, you have a "document" which is the main object ("gamePlayer") that is being displayed. Each Frame is a view of that document.