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Date: Mon, 23 Jan 2012 20:58:18 +0000
From: MRAB <python@mrabarnett.plus.com>
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To: python-list@python.org
Subject: Re: Using an object inside a class
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On 23/01/2012 20:27, Jonno wrote:
>
>
> On Mon, Jan 23, 2012 at 2:09 PM, Ian Kelly <ian.g.kelly@gmail.com
> <mailto:ian.g.kelly@gmail.com>> wrote:
>
>     On Mon, Jan 23, 2012 at 12:44 PM, Jonno <jonnojohnson@gmail.com
>     <mailto:jonnojohnson@gmail.com>> wrote:
>      > I have a pretty complicated bit of code that I'm trying to
>     convert to more
>      > clean OOP.
>
>     Then you probably should not be using globals.
>
>
> I'm trying to rewrite the whole thing to get rid of my globals.
>
>
>      > Without getting too heavy into the details I have an object which
>     I am
>      > trying to make available inside another class. The reference to
>     the object
>      > is rather long and convoluted but what I find is that within my class
>      > definition this works:
>      >
>      > class Class1:
>      >     def __init__(self):
>      >
>      >     def method1(self):
>      >          foo.bar.object
>      >
>      > But this tells me "global name foo is not defined":
>      >
>      > class Class1:
>      >      def __init__(self):
>      >            foo.bar.object
>
>     Where is foo actually stored?  Is it in fact a global, or is it
>     somewhere else?  Please post the actual code.  I suspect that what's
>     going on here is that you're assigning foo somewhere inside method1
>     and so it is actually a local variable to that method, but there is no
>     way to know that for certain from the minimal snippet provided.
>
> The whole code is complex but here is where I define foo and bar:
>
> class MyApp(wx.App):
>      def OnInit(self):
>          self.bar = MyFrame(None, -1, 'App Name')
>          self.bar.Show(True)
>          return True
> foo = MyApp(0)
> app.MainLoop()
>
> There is nothing inside method1 except the foo.bar.object reference.
>
>      > Obviously I want the object to be available throughout the class
>     (I left out
>      > the self.object = etc for simplicity).
>
>     Do you mean that you want the same object to be available to all
>     instances of Class1, or that you just want the object to be available
>     to all methods within a single instance (and other instances might
>     access other objects)?  In the first case, I would recommend storing
>     foo in a class attribute; in the second case, an instance attribute.
>     Either way, it would then be accessed simply as "self.foo".
>
>
> Either way would work but the main issue is I can't seem to use foo or
> foo.bar or foo.bar.object anywhere in __init__ or even before that in
> the main class area.
>
This line:

foo = MyApp(0)

will create a 'MyApp' instance and then bind it to the name 'foo'.
Until that binding occurs, the name 'foo' doesn't exist.