Python (tkinter) entry variable

Question

I'm making some program in tkinter and I got one problem.

In tkinter entry if I put 1 textvariable name in both of entry it will show instant on both of entries like this:

But I want to right entry immediately multiplied with 500. So If I put 2 on left it should show 1000 on right.

Label(frame2, foreground="#E3AAD5", text="500e").grid(row=0, column=0, sticky=W, padx=10) # Kreira label (opis kućice pokraj) 
    v_500 = IntVar()
    _500 = Entry(frame2, textvariable=v_500)
    _500.grid(row=0, column=1, sticky=W)

    Entry(frame2, textvariable=v_500*500).grid(row=0, column=2, sticky=W)

But it doesn't work.

TypeError: unsupported operand type(s) for *: 'instance' and 'int' — user3508675
– user3508675, Commented Aug 21, 2015 at 11:58

Bryan Oakley · Accepted Answer · 2015-08-21 13:00:47Z

2

There is no direct support for what you want. That being said, what you want to do is fairly easy. IntVars can be configured to call a function when they change. You can use this callback to do the multiplication and update the widget.

For example:

def update_other_label(name1, name2, mode):
    value = v_500.get()
    product = value * 500
    v_500_mult.set(product)

v_500 = IntVar()
v_500.trace("w", update_other_label)
v_500_mult = Intvar()
...
_500 = Entry(frame2, textvariable=v_500)
Entry(frame2, textvariable=v_500_mult).grid(row=0, column=2, sticky=W)

You don't have to use an IntVar for the second entry if you don't want -- you can directly modify the entry widget if you keep a reference. I didn't do it that way since you aren't keeping a reference.

answered Aug 21, 2015 at 13:00

Bryan Oakley

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2 Comments

Bryan Oakley Over a year ago

@CheckThisOut: that's what Tkinter requires. It allows you to use the same callback for multiple variables and modes, and to know which variable and which mode triggered the callback.

user3508675 Over a year ago

Okay, thank you. But what If I have more variables for multiply, not only 500. I need to multiply 10 variables with 1 definition. I don't want to mess up with vars cuz it's program for counting.

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