# tkinter --- Python interface to Tcl/Tk — Coupling widget variables

> ^^^^^^^^^^^^^^^^^^^^^^^^^ Some widgets can tie their current value directly to a program variable, so that the two stay in sync.

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- Updated: `2026-08-16T09:31:35.319027+00:00`
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^^^^^^^^^^^^^^^^^^^^^^^^^

Some widgets can tie their current value directly to a program variable, so that the two stay in sync. Options such as variable, textvariable, value, onvalue and offvalue set up this connection: when the user changes the widget the variable is updated, and when the variable is set the widget redraws to match.

A widget can be linked only to a Variable object, not to an ordinary Python variable. This is not a limitation of !tkinter but a consequence of how the two languages differ: the link relies on Tcl being notified every time the value changes, and Python offers no way to react when a plain variable is reassigned. A Variable sidesteps this by keeping its value inside the Tcl interpreter and exposing it through explicit ~Variable.get and ~Variable.set methods.

Ready-made subclasses cover the common types: StringVar, IntVar, DoubleVar and BooleanVar. Pass one as a widget's textvariable (or variable) option, then read and update it with ~Variable.get and ~Variable.set; the widget tracks it with no further work on your part.

Keep a reference to the variable for as long as the widget uses it -- for example by storing it as an attribute. A Variable that is garbage collected removes its underlying Tcl variable, breaking the connection to the widget (see Variable).

import tkinter as tk from tkinter import ttk

# Create the application variable and give it an initial value. contents = tk.StringVar(value="this is a variable")

# Tell the entry widget to track the variable. entry = ttk.Entry(root, textvariable=contents) entry.pack()

# Print the current value whenever the user presses Return. def print_contents(event): print("The current entry content is:", contents.get())

entry.bind("", print_contents)

# Setting the variable from the program updates the entry through the # same link. def clear(): contents.set("")

ttk.Button(root, text="Clear", command=clear).pack()

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