Set a default value for a ttk Combobox
Solution 1
The problem is that the instance of StringVar is getting garbage-collected. This is because it's a local variable due to how you wrote your code.
One solution is to use a class so that your StringVar persists:
from tkinter import Tk, StringVar, ttk
class Application:
def __init__(self, parent):
self.parent = parent
self.combo()
def combo(self):
self.box_value = StringVar()
self.box = ttk.Combobox(self.parent, textvariable=self.box_value,
state='readonly')
self.box['values'] = ('A', 'B', 'C')
self.box.current(0)
self.box.grid(column=0, row=0)
if __name__ == '__main__':
root = Tk()
app = Application(root)
root.mainloop()
Solution 2
When your function 'combo' exits, the local variable 'value' is destroyed. You need a persistent variable, such as a global variable or a variable that is a property of a class so that the value isn't garbage-collected while the widget still exists.
Solution 3
The get()
method can be used within your function to rename the StringVar
and save it under another name to avoid losing it altogether via garbage collection.
value = StringVar()
keepvalue = value.get()
then use keepvalue
instead of value:
box = ttk.Combobox(root, textvariable=keepvalue, state='readonly')
This had 'A' showing in the combobox for me.
kynikos
Updated on April 04, 2020Comments
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kynikos about 4 years
I'm using Python 3.2.1 in Arch Linux x86_64. This one is really driving me crazy: I just want to have a default, preselected value for a
ttk.Combobox
as soon as I grid it. This is my code:from tkinter import Tk, StringVar, ttk root = Tk() def combo(parent): value = StringVar() box = ttk.Combobox(parent, textvariable=value, state='readonly') box['values'] = ('A', 'B', 'C') box.current(0) box.grid(column=0, row=0) combo(root) root.mainloop()
Which draws an empty
Combobox
. What's funny is that if I don't use a function it works perfectly:from tkinter import Tk, StringVar, ttk root = Tk() value = StringVar() box = ttk.Combobox(root, textvariable=value, state='readonly') box['values'] = ('A', 'B', 'C') box.current(0) box.grid(column=0, row=0) root.mainloop()
Of course, in the real program I have to use a function, so I need another solution.
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kynikos almost 13 yearsThank you, it works perfectly! Actually I was using a class in my app, but I was using a local variable for
box_value
; withself.box_value
it does the trick ;) -
kynikos almost 13 yearsThanks for the technical explanation ^^
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texasman1979 almost 9 yearsSorry to jump in, but when i import ttk, It doesn't recognize "Combobox" as a option or widget. Any ideas?
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Eryk Sun almost 9 years@texasman1979, which version of Python are you using, and which OS? Check
ttk.__file__
to make sure it's the rightttk
module. -
Jalkhov over 3 yearsIts possible set the current item by value? Example:
self.box.current("Dubai")