Re: main window in tkinter app
William Gill wrote:
> That does it!, thanks.
>
> Thinking about it, when I created a derived class with an __init__
> method, I overrode the base class's init. It should have been
> intuitive that I needed to explicitly call baseclass.__init(self), it
> wasn't. It might have hit me if the fault was related to someting in
> baseclass.__init() not taking place, but the recursion loop didn't give
> me a clue. Any idea why failing to init the base class caused the loop?
You never pasted the first part of the traceback:
File "", line 1, in -toplevel-
app.title('frob')
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1531, in wm_title
return self.tk.call('wm', 'title', self._w, string)
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1654, in __getattr__
return getattr(self.tk, attr)
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1654, in __getattr__
return getattr(self.tk, attr)
When you didn't call Tk.__init__(self), self.tk was never initialized.
Further, it's obvious from the traceback that Tk implements a
__getattr__ method; from the python docs:
__getattr__(self,name): Called when an attribute lookup has not found
the attribute in the usual places
Since self.tk doesn't exist, __getattr__(self,tk) was called. Without
looking at the TKinter source code, we can surmise that there's a
default behavior of "if self doesn't have it, return the relevant
attribute from within self.tk." The problem, of course, arises when
self.tk doesn't exist -- this causes the self.tk reference to call
self.__getattr__('tk'), which is recursive.
The infinite recursion, then, is a mild bug in TKinter that doesn't show
itself during normal use. The proper solution should be to replace the
self.tk call with either self.__dict__['tk'], or to make Tk a new-style
class and use object.__getattribute__(self,'tk'). (Note: there are
probably some fine details that I'm missing in this 'solution', so take
it with a potato-sized grain of salt. The general principle still
applies though.)
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Re: main window in tkinter app
That does it!, thanks.
Thinking about it, when I created a derived class with an __init__
method, I overrode the base class's init. It should have been
intuitive that I needed to explicitly call baseclass.__init(self), it
wasn't. It might have hit me if the fault was related to someting in
baseclass.__init() not taking place, but the recursion loop didn't give
me a clue. Any idea why failing to init the base class caused the loop?
Bill
Christopher Subich wrote:
> William Gill wrote:
>
>> O.K. I tried from scratch, and the following snippet produces an
>> infinite loop saying:
>>
>> File "C:\Python24\lib\lib-tk\Tkinter.py", line 1647, in __getattr__
>> return getattr(self.tk, attr)
>>
>> If I comment out the __init__ method, I get the titled window, and
>> print out self.var ('1')
>>
>>
>> import os
>> from Tkinter import *
>>
>> class MyApp(Tk):
>> var=1
>> def __init__(self):
>> pass
>> def getval(self):
>> return self.var
>>
>>
>> app = MyApp()
>>
>> app.title("An App")
>> print app.getval()
>> app.mainloop()
>
>
> You're not calling the parent's __init__ inside your derived class. I
> would point out where the Python Tutorial points out that you should do
> this, but it's not in the obvious place (Classes: Inheritance).
>
> Python does -not- automagically call parent-class __init__s for derived
> classes, you must do that explicitly. Changing the definition of your
> class to the following works:
> >>> class MyApp(Tk):
> var=1
> def __init__(self):
> Tk.__init__(self)
> pass
> def getval(self):
> return self.var
>
> It works when you comment out __init__ because of a quirk in Python's
> name resolution. As you'd logically expect, if you don't define a
> function in a derived class but call it (such as instance.method()), it
> will call the method from the base class.
>
> You just proved that this works for __init__ methods also. When you
> didn't define __init__ for your derived class, MyApp() called
> Tk.__init__(), which Does the Right Thing in terms of setting up all the
> specific Tkinter-specific members.
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Re: main window in tkinter app
William Gill wrote:
> O.K. I tried from scratch, and the following snippet produces an
> infinite loop saying:
>
> File "C:\Python24\lib\lib-tk\Tkinter.py", line 1647, in __getattr__
> return getattr(self.tk, attr)
>
> If I comment out the __init__ method, I get the titled window, and print
> out self.var ('1')
>
>
> import os
> from Tkinter import *
>
> class MyApp(Tk):
> var=1
> def __init__(self):
> pass
> def getval(self):
> return self.var
>
>
> app = MyApp()
>
> app.title("An App")
> print app.getval()
> app.mainloop()
You're not calling the parent's __init__ inside your derived class. I
would point out where the Python Tutorial points out that you should do
this, but it's not in the obvious place (Classes: Inheritance).
Python does -not- automagically call parent-class __init__s for derived
classes, you must do that explicitly. Changing the definition of your
class to the following works:
>>> class MyApp(Tk):
var=1
def __init__(self):
Tk.__init__(self)
pass
def getval(self):
return self.var
It works when you comment out __init__ because of a quirk in Python's
name resolution. As you'd logically expect, if you don't define a
function in a derived class but call it (such as instance.method()), it
will call the method from the base class.
You just proved that this works for __init__ methods also. When you
didn't define __init__ for your derived class, MyApp() called
Tk.__init__(), which Does the Right Thing in terms of setting up all the
specific Tkinter-specific members.
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Re: main window in tkinter app
It also seems to operate the same with or without " app.mainloop()". Is
an explicit call to mainloop needed?
William Gill wrote:
> O.K. I tried from scratch, and the following snippet produces an
> infinite loop saying:
>
> File "C:\Python24\lib\lib-tk\Tkinter.py", line 1647, in __getattr__
> return getattr(self.tk, attr)
>
> If I comment out the __init__ method, I get the titled window, and print
> out self.var ('1')
>
>
> import os
> from Tkinter import *
>
> class MyApp(Tk):
> var=1
> def __init__(self):
> pass
> def getval(self):
> return self.var
>
>
> app = MyApp()
>
> app.title("An App")
> print app.getval()
> app.mainloop()
>
>
> Eric Brunel wrote:
>
>> On Mon, 18 Jul 2005 16:57:51 GMT, William Gill <[EMAIL PROTECTED]>
>> wrote:
>>
>>> A short while ago someone posted that(unlike the examples) you should
>>> use Tk as the base for your main window in tkinter apps, not Frame.
>>> Thus :
>>>
>>>class MyMain(Frame):
>>>def __init__(self, master):
>>>self.root = master
>>>self.master=master
>>>self.createWidgets()
>>>def createWidgets():
>>> ...
>>>root = Tk()
>>>app = MyMain(root)
>>>app.master.title("Object Editor")
>>>root.mainloop()
>>>
>>> would become:
>>>
>>> class MyMain(Tk):
>>>...
>>>...
>>> app = MyMain()
>>> app.title("My App")
>>> app.mainloop()
>>>
>>> When I try converting to this approach I run into a problem with the
>>> __init__() method. It appears to go into an infinite loop in
>>> tkinter.__getattr__().
>>
>>
>> [...]
>>
>> I never ran into this problem. Can you please post a short script
>> showing this behavior? Without knowing what you exactly do in your
>> __init__ and createWidgets method, it's quite hard to figure out what
>> happens...
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Re: main window in tkinter app
O.K. I tried from scratch, and the following snippet produces an
infinite loop saying:
File "C:\Python24\lib\lib-tk\Tkinter.py", line 1647, in __getattr__
return getattr(self.tk, attr)
If I comment out the __init__ method, I get the titled window, and print
out self.var ('1')
import os
from Tkinter import *
class MyApp(Tk):
var=1
def __init__(self):
pass
def getval(self):
return self.var
app = MyApp()
app.title("An App")
print app.getval()
app.mainloop()
Eric Brunel wrote:
> On Mon, 18 Jul 2005 16:57:51 GMT, William Gill <[EMAIL PROTECTED]> wrote:
>
>> A short while ago someone posted that(unlike the examples) you should
>> use Tk as the base for your main window in tkinter apps, not Frame.
>> Thus :
>>
>>class MyMain(Frame):
>>def __init__(self, master):
>>self.root = master
>>self.master=master
>>self.createWidgets()
>>def createWidgets():
>> ...
>>root = Tk()
>>app = MyMain(root)
>>app.master.title("Object Editor")
>>root.mainloop()
>>
>> would become:
>>
>> class MyMain(Tk):
>>...
>>...
>> app = MyMain()
>> app.title("My App")
>> app.mainloop()
>>
>> When I try converting to this approach I run into a problem with the
>> __init__() method. It appears to go into an infinite loop in
>> tkinter.__getattr__().
>
> [...]
>
> I never ran into this problem. Can you please post a short script
> showing this behavior? Without knowing what you exactly do in your
> __init__ and createWidgets method, it's quite hard to figure out what
> happens...
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Re: main window in tkinter app
> I never ran into this problem. ...
O.K. That, means I probably have something else wrong. I will need to
start with a 'clean slate' instead of trying to modify existing code.
It's getting to convoluted to follow anyway after all the cobbling I've
done.
If I get a repeat of the original problem I will post the code and the
exact error message, but at least now I know It SHOULD work.
Thanks
Bill,
Eric Brunel wrote:
> On Mon, 18 Jul 2005 16:57:51 GMT, William Gill <[EMAIL PROTECTED]> wrote:
>
>> A short while ago someone posted that(unlike the examples) you should
>> use Tk as the base for your main window in tkinter apps, not Frame.
>> Thus :
>>
>>class MyMain(Frame):
>>def __init__(self, master):
>>self.root = master
>>self.master=master
>>self.createWidgets()
>>def createWidgets():
>> ...
>>root = Tk()
>>app = MyMain(root)
>>app.master.title("Object Editor")
>>root.mainloop()
>>
>> would become:
>>
>> class MyMain(Tk):
>>...
>>...
>> app = MyMain()
>> app.title("My App")
>> app.mainloop()
>>
>> When I try converting to this approach I run into a problem with the
>> __init__() method. It appears to go into an infinite loop in
>> tkinter.__getattr__().
>
> [...]
>
> I never ran into this problem. Can you please post a short script
> showing this behavior? Without knowing what you exactly do in your
> __init__ and createWidgets method, it's quite hard to figure out what
> happens...
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Re: main window in tkinter app
On Mon, 18 Jul 2005 16:57:51 GMT, William Gill <[EMAIL PROTECTED]> wrote:
> A short while ago someone posted that(unlike the examples) you should
> use Tk as the base for your main window in tkinter apps, not Frame. Thus :
>
>class MyMain(Frame):
>def __init__(self, master):
>self.root = master
>self.master=master
>self.createWidgets()
>def createWidgets():
> ...
>root = Tk()
>app = MyMain(root)
>app.master.title("Object Editor")
>root.mainloop()
>
> would become:
>
> class MyMain(Tk):
>...
>...
> app = MyMain()
> app.title("My App")
> app.mainloop()
>
> When I try converting to this approach I run into a problem with the
> __init__() method. It appears to go into an infinite loop in
> tkinter.__getattr__().
[...]
I never ran into this problem. Can you please post a short script showing this
behavior? Without knowing what you exactly do in your __init__ and
createWidgets method, it's quite hard to figure out what happens...
--
python -c "print ''.join([chr(154 - ord(c)) for c in
'U(17zX(%,5.zmz5(17;8(%,5.Z65\'*9--56l7+-'])"
--
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main window in tkinter app
A short while ago someone posted that(unlike the examples) you should
use Tk as the base for your main window in tkinter apps, not Frame. Thus :
class MyMain(Frame):
def __init__(self, master):
self.root = master
self.master=master
self.createWidgets()
def createWidgets():
...
root = Tk()
app = MyMain(root)
app.master.title("Object Editor")
root.mainloop()
would become:
class MyMain(Tk):
...
...
app = MyMain()
app.title("My App")
app.mainloop()
When I try converting to this approach I run into a problem with the
__init__() method. It appears to go into an infinite loop in
tkinter.__getattr__().
If I omit __init__() I get a properly titled window, but must explicitly
call my createWidgets method from __main__.
class MyMain(Tk):
createWidgets()
...
...
app = MyMain()
app.title("My App")
app.createWidgets()
app.mainloop()
Am I missing something?
Bill
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