Using StringVars in List of Dictionaries as tkInter variables forScale and Label widgets


S

seanacais

I'm trying to build an unknown number of repeating gui elements
dynamically so I need to store the variables in a list of
dictionaries. I understand that Scale "variable" name needs to be a
StringVar but I cannot figure out how to initialize the dictionary.

I've tried the following code

ps = PowerSupply() # Instantiate a Power Supply VM Object
numOPs = ps.getOnum() # Find the number of outputs
OPValues = [] # Global list to hold one dictionary per output

for c in range(numOPs):
OPValues.append({ })
ps.initOPValues(c, OPValues[c])



ps.initOPValues is defined as follows:

def initOPValues(self, OPname, dname):

OPDefaults = {
'Vval' : 0,
'Ival' : 0,
'Otemp' : 0
}

dname = dict((d,StringVar()) for d in OPDefaults)
for d in OPDefaults:
dname[d].set(OPDefaults[d])

I get the following error:

Traceback (most recent call last):
File "C:\Code\gui\tkinter.py", line 165, in <module>
ps.initOPValues(c, OPValues[c])
File "C:\Code\gui\tkinter.py", line 47, i initOPValues
dname = dict((d,StringVar()) for d in OPDefaults)
File "C:\Code\gui\tkinter.py", line 47, in <genexpr>
dname = dict((d,StringVar()) for d in OPDefaults)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 254, in __init__
Variable.__init__(self, master, value, name)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 185, in __init__
self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk'
Exception exceptions.AttributeError: "StringVar instance has no
attribute '_tk'"
in <bound method StringVar.__del__ of <Tkinter.StringVar instance at
0x00B7D468>> ignored

Any help is appreciated!

Thanks,

Kevin
 
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P

Peter Otten

seanacais said:
I'm trying to build an unknown number of repeating gui elements
dynamically so I need to store the variables in a list of
dictionaries. I understand that Scale "variable" name needs to be a
StringVar but I cannot figure out how to initialize the dictionary.

I've tried the following code

ps = PowerSupply() # Instantiate a Power Supply VM Object
numOPs = ps.getOnum() # Find the number of outputs
OPValues = [] # Global list to hold one dictionary per output

for c in range(numOPs):
OPValues.append({ })
ps.initOPValues(c, OPValues[c])



ps.initOPValues is defined as follows:

def initOPValues(self, OPname, dname):

OPDefaults = {
'Vval' : 0,
'Ival' : 0,
'Otemp' : 0
}

dname = dict((d,StringVar()) for d in OPDefaults)
for d in OPDefaults:
dname[d].set(OPDefaults[d])

I get the following error:

Traceback (most recent call last):
File "C:\Code\gui\tkinter.py", line 165, in <module>
ps.initOPValues(c, OPValues[c])
File "C:\Code\gui\tkinter.py", line 47, i initOPValues
dname = dict((d,StringVar()) for d in OPDefaults)
File "C:\Code\gui\tkinter.py", line 47, in <genexpr>
dname = dict((d,StringVar()) for d in OPDefaults)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 254, in __init__
Variable.__init__(self, master, value, name)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 185, in __init__
self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk'
Exception exceptions.AttributeError: "StringVar instance has no
attribute '_tk'"
in <bound method StringVar.__del__ of <Tkinter.StringVar instance at
0x00B7D468>> ignored

Any help is appreciated!

There's some magic going on behind the scene which means that you have to
create a Tkinter.Tk instance before you can start churning out StringVars:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 257, in __init__
Variable.__init__(self, master, value, name)
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 188, in __init__
self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk''42'

Peter
 
S

seanacais

There's some magic going on behind the scene which means that you have to
create a Tkinter.Tk instance before you can start churning out StringVars:


Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 257, in __init__
Variable.__init__(self, master, value, name)
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 188, in __init__
self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk'>>> root = tk.Tk()

'42'

Peter


I had the Tkinter import as

from Tkinter import * but I changed it to

import Tkinter as tk

and modified the creation of the root object to

root=tk.Tk()

I then had to change every instance of Menu, Label,
Button, and all Tkinter elements to be prefaced by
tk. (so Button became tk.Button). That kind of makes
sense to me.

However even after specifying StringVar is a tk type

def initOPValues(self, OPname, dname):

OPDefaults = {
'Vval' : 0,
'Ival' : 0,
'Otemp' : 0
}

dname = dict((d,tk.StringVar()) for d in OPDefaults)
for d in OPDefaults:
dname[d].set(OPDefaults[d])


I still get a very similar error message

C:\Code\gui>tkinter.py
Traceback (most recent call last):
File "C:\Code\gui\tkinter.py", line 169, in <module>
ps.initOPValues(c, OPValues[c])
File "C:\Code\gui\tkinter.py", line 54, in initOPValues
dname = dict((d,tk.StringVar()) for d in OPDefaults)
File "C:\Code\gui\tkinter.py", line 54, in <genexpr>
dname = dict((d,tk.StringVar()) for d in OPDefaults)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 254, in __init__
Variable.__init__(self, master, value, name)
File "C:\Python25\lib\lib-tk\Tkinter.py", line 185, in __init__
self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk'
Exception exceptions.AttributeError: "StringVar instance has no
attribute '_tk'"
in <bound method StringVar.__del__ of <Tkinter.StringVar instance at
0x00B7E418>> ignored


Thanks!

Kevin
 
P

Peter Otten

seanacais said:
I had the Tkinter import as

from Tkinter import * but I changed it to

import Tkinter as tk

and modified the creation of the root object to

root=tk.Tk()

I then had to change every instance of Menu, Label,
Button, and all Tkinter elements to be prefaced by
tk. (so Button became tk.Button). That kind of makes
sense to me.

However even after specifying StringVar is a tk type

You misunderstood. There is no such thing as a "tk type".
Whether you use

from Tkinter import *

or

import Tkinter as tk

is irrelevant for the problem at hand.
def initOPValues(self, OPname, dname):

OPDefaults = {
'Vval' : 0,
'Ival' : 0,
'Otemp' : 0
}

dname = dict((d,tk.StringVar()) for d in OPDefaults)
for d in OPDefaults:
dname[d].set(OPDefaults[d])


I still get a very similar error message

You have to ensure that the lines

from Tkinter import *
root = Tk()

are *executed* before the line

dname = dict((d, StringVar()) for d in OPDefaults)

While I prefer the alternative

import Tkinter as tk
root = tk.Tk()
# ...
dname = dict((d, tk.StringVar()) for d in OPDefaults)

this is just a matter of style.

Peter

PS: If you still can't fix your script, please post it completely or,
better, a small self-contained (runnable) script showing the same problem
 
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S

seanacais

seanacais wrote:

You have to ensure that the lines

from Tkinter import *
root = Tk()

are *executed* before the line

dname = dict((d, StringVar()) for d in OPDefaults)

Peter

PS: If you still can't fix your script, please post it completely or,
better, a small self-contained (runnable) script showing the same problem

I had looked for that, but didn't see it. After reading your post I
went back
to look again. Indeed, the initOPValues() function was being called
before
the root=Tk(). I've fixed the order of the calls and my script is
behaving
exactly as I expect now. Thank you for taking the time to help me.

Kevin
 

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