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    <p>It's a little bit unclear what you mean by "pass parameters to my callback function." You're already doing that! For example: </p> <pre><code>from Tkinter import * def callbackfunc(*args, **kwargs): print args, kwargs print "Hello World!" class App(object): def __init__(self, master): frame = Frame(master) frame.pack() optionvalue = IntVar(master) optionvalue.set(2) optionvalue.trace("w", callbackfunc) self.optionmenu = OptionMenu(master, optionvalue, 1, 2, 3, 4) self.optionmenu.pack() root = Tk() app = App(root) root.mainloop() </code></pre> <p>When run...</p> <pre><code>$ python foo.py ('PY_VAR0', '', 'w') {} Hello World! </code></pre> <p>So you see, when Tkinter calls your callback, it passes parameters to it. If you wanted to do something other than print them, you could store them in some state, by passing a method instead of a function. </p> <pre><code>from Tkinter import * class App(object): def __init__(self, master): frame = Frame(master) frame.pack() optionvalue = IntVar(master) optionvalue.set(2) optionvalue.trace("w", self.callbackfunc) self.optionmenu = OptionMenu(master, optionvalue, 1, 2, 3, 4) self.optionmenu.pack() self.state = [] def callbackfunc(self, *args): self.state.append(args) print self.state root = Tk() app = App(root) root.mainloop() </code></pre> <p>When run...</p> <pre><code>$ python foo.py [('PY_VAR0', '', 'w')] [('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w')] [('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w')] </code></pre> <p>Also, perhaps you want to access the value of <code>optionvalue</code>. You could save a reference to it then: </p> <pre><code>from Tkinter import * class App(object): def __init__(self, master): frame = Frame(master) frame.pack() self.optionvalue = IntVar(master) self.optionvalue.set(2) self.optionvalue.trace("w", self.callbackfunc) self.optionmenu = OptionMenu(master, self.optionvalue, 1, 2, 3, 4) self.optionmenu.pack() self.state = [] def callbackfunc(self, *args): self.state.append(args) print self.state print self.optionvalue.get() root = Tk() app = App(root) root.mainloop() </code></pre> <p>When run...</p> <pre><code>$ python foo.py [('PY_VAR0', '', 'w')] 1 [('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w')] 2 [('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w'), ('PY_VAR0', '', 'w')] 3 </code></pre> <p>You could also use <code>root.getvar(name)</code> with <code>name = 'PY_VAR0'</code> (the first arg passed to the callback), as <a href="https://stackoverflow.com/a/9869270/577088">noob oddy</a> suggests.</p>
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    1. POWhat are the limitations of callback functions associated with Tkinter traces?
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    1. COYou are right, I did not make perfect sense. I meant to say "additional" parameters...which is what you passed with "**kwargs" in your first example. Although, I was also confused about how to pass parameters within the trace (when you write "w", callbackfunc). I cannot pass anything to callbackfunc that way right?
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    2. CO@nairware, you can't pass anything to callbackfunc that way, because you aren't _calling_ the function. It's a callback, which means that only _Tkinter_ ever calls it, and only passes to it the things that you see above. `**kwargs` was not an "additional parameter" -- it's just the keyword version of `*args` (i.e. it accepts [keyword rather than positional arguments](http://stackoverflow.com/questions/1419046/python-normal-arguments-vs-keyword-arguments). Furthermore, using `*args` accepts all "additional parameters" that get thrown at it (by Tkinter).
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    3. CO@nairware, what you _can_ do, and perhaps what you mean to do, is create a function that _returns_ a function, pass a parameter to that function, and pass the returned function as the callback. If that's something you want to do, let me know.
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