I create a tkinter root :

```
root = tkinter.Tk()

```

and would like to create a *dynamic* variable which would be always linked to some property (or is it called a method?) of `root` :

```
X = root.winfo_width()

```

If `root`'s `winfo_width()` changes, I would like that `X` is automatically updated. 

How to do this?
 Is it called an alias ? a dynamic variable ?