Set tkinter Entry default value

Question

I'm developing a script that will build GUIs automatically after reading a python script. I'm having problems in getting the Entry objects that I build to accept a default value.

I pass my method a dictionary (arg) which contains a default value and a variable name.

def create_entry(self,
                 arg):

    if 'default' in arg.keys():
        var = StringVar(value=arg['default'])
    else:
        var = StringVar()
    box = ttk.Entry(self.mainframe, textvariable=var)
    box.grid(column=1, row=self.num, columnspan=2, sticky=(W, E))
    label= ttk.Label(self.mainframe, text=arg['name']).grid(column=0, row=self.num, sticky=E)

    return box, label

The thing I can't explain is that a similar method for looking up directories works fine....

def create_askdirectory(self,
                        arg):

    if 'default' in arg.keys():
        var = StringVar(value=arg['default'])
    else:
        var = StringVar()
    box = ttk.Entry(self.mainframe, textvariable=var)
    box.grid(column=1, row=self.num, columnspan=2, sticky=(W, E))

    def askdirectory():
        dirname = filedialog.askdirectory()
        if dirname:
            var.set(dirname)

    button = ttk.Button(self.mainframe, text='directory', command=askdirectory).grid(column=0, row=self.num)

    return box, button

That whole `if..else` could just be `var = StringVar(value=arg.get('default', ''))`. — TigerhawkT3, Apr 27 '16 at 11:01

score 6 · Accepted Answer · edited Feb 02 '21 at 10:09

6

ttk widgets are more sensitive to garbage collection than tkinter widgets. Your variables (which you don't actually need) are local variables, so they are getting garbage collected.

The reason that it works in the other code is that the askdirectory function is inside the create_askdirectory function so it is able to see the local variables.

My advice is to not use StringVar -- in this case they are completely unnecessary.

box = ttk.Entry(self.mainframe)
box.insert(0, arg.get("default", ""))

edited Feb 02 '21 at 10:09

Amin Khodamoradi

392
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answered Apr 27 '16 at 11:54

Bryan Oakley

370,779
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685

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Amazing, thanks! Had to chop the first line to box = ttk.Entry(self.mainframe) – WRJ Apr 27 '16 at 12:31
Kudos. I never would have guessed this was related to garbage collection. – Edward Falk May 12 '21 at 19:30

Set tkinter Entry default value

1 Answers1