How to use a widget name from a validator function?

Question

I found this code: Interactively validating Entry widget content in tkinter

import tkinter as tk  # python 3.x
# import Tkinter as tk # python 2.x

class Example(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        # valid percent substitutions (from the Tk entry man page)
        # note: you only have to register the ones you need; this
        # example registers them all for illustrative purposes
        #
        # %d = Type of action (1=insert, 0=delete, -1 for others)
        # %i = index of char string to be inserted/deleted, or -1
        # %P = value of the entry if the edit is allowed
        # %s = value of entry prior to editing
        # %S = the text string being inserted or deleted, if any
        # %v = the type of validation that is currently set
        # %V = the type of validation that triggered the callback
        #      (key, focusin, focusout, forced)
        # %W = the tk name of the widget

        vcmd = (self.register(self.onValidate),
                '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')
        self.entry = tk.Entry(self, validate="key", validatecommand=vcmd)
        self.text = tk.Text(self, height=10, width=40)
        self.entry.pack(side="top", fill="x")
        self.text.pack(side="bottom", fill="both", expand=True)

    def onValidate(self, d, i, P, s, S, v, V, W):
        self.text.delete("1.0", "end")
        self.text.insert("end","OnValidate:\n")
        self.text.insert("end","d='%s'\n" % d)
        self.text.insert("end","i='%s'\n" % i)
        self.text.insert("end","P='%s'\n" % P)
        self.text.insert("end","s='%s'\n" % s)
        self.text.insert("end","S='%s'\n" % S)
        self.text.insert("end","v='%s'\n" % v)
        self.text.insert("end","V='%s'\n" % V)
        self.text.insert("end","W='%s'\n" % W)

        # Disallow anything but lowercase letters
        if S == S.lower():
            return True
        else:
            self.bell()
            return False

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

I need to use the instance (%W) but it is a string. I need something like this:

import tkinter as tk  # python 3.x
# import Tkinter as tk # python 2.x

class Example(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        vcmd = (self.register(self.onValidate),
                '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')
        self.entry = tk.Entry(self, validate="key", validatecommand=vcmd)
        self.text = tk.Text(self, height=10, width=40)
        self.entry.pack(side="top", fill="x")
        self.text.pack(side="bottom", fill="both", expand=True)

    def onValidate(self, d, i, P, s, S, v, V, W):
        print type(W) #This gives <string>
        W = instance(W) #Something to convert the string to an instance like int()
        W.get()
        W.insert('Some text',0)

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

I need a way to modify the widget that has attached the valitation function because the register method only gives the path or the pointer of the widget as a string. But I need to modify the widget.

I have been thinking to put all widgets in a list named "instance", and then make a "for w in instances" and compare all widgets with %W of the validator function, until it finds the same widget name, and then modify the objet in the list.

Is there a way to do this easier? Thank you guys!

score 1 · Answer 1 · answered Sep 18 '17 at 02:12

The validation function is not designed for you to modify the contents of the widget during validation.

From the canonical tcl/tk documentation:

The validate option will also set itself to none when you edit the entry widget from within either the validateCommand or the invalidCommand. Such editions will override the one that was being validated. If you wish to edit the entry widget (for example set it to {}) during validation and still have the validate option set, you should include the command

That being said, if you need to, you can convert the widget name to a widget reference using the method nametowidget which you can call via any widget.

def onValidate(self, d, i, P, s, S, v, V, W):
    widget = self.nametowidget(W)
    ...

How to use a widget name from a validator function?

1 Answers1