Access widget by widget / window name Tk

I use validatecommand

to observe and validate the input widget "dynamically".

Standard usage validatecommand

prevents invalid characters from being entered into the observed input widget. This is not the behavior I like, so I used validatecommand

to pass the record widget string to another function and return True

anyway. floatstr_to_float

checks a string using a regular expression preg

.

If the regex matches the entered value, everything is fine, and therefore executed print('approved')

. However, if the user has entered an invalid input, the regex does not match, is executed print('not approved')

, and the corresponding input widget should be filled with red (color change has not yet been properly implemented).

What I have done so far is changing the background of the very first input widget with a help <widget>.config(bg=<background>)

to check that I can access each widget by indexing the list of all the widgets I have created.

validatecommand

can pass multiple arguments to the function being executed (e.g. input / text string and widget / window name). So getting a link to an invalid widget is not a problem at all. However, the path passed validatecommand

is not python accessible. How can I get a reference (like a unique variable name) from this pathname to change the background by executing <widget>.config(bg=<background>)

in widgets containing (in) valid input?

- MWE -

#!/usr/bin/env python3
# -*- coding: <utf-8> -*-

# code adapted from:
# http://stackoverflow.com/questions/4140437/python-tkinter-interactively-validating-entry-widget-content

import tkinter as tk
import re

class MyApp():
    def __init__(self):
        self.root = tk.Tk()
        self.parameternames = [
            ('a', 'U'), ('b', 'U'), ('c', 'U'), ('d', 'U'), ('e', 'U'),
            ('f', 'U'), ('g', 'U'), ('h', 'U'), ('i', 'U'), ('j', 'U'),
            ('k', 'U'), ('l', 'U'), ('m', 'U'), ('n', 'U'), ('o', 'U'),
            ('p', 'U'), ('q', 'U'), ('r', 'U'), ('s', 'U'), ('t', 'U')]
        self.vcmd = (self.root.register(self.OnValidate), '%P', '%W')
        self.create_widgets()

    def create_widgets(self):
        self.entries = []
        for i in enumerate(self.parameternames):
            entry = tk.Entry(self.root, validate="all", validatecommand=self.vcmd)
            self.default_bg = entry.cget("bg")
            entry.pack()
            self.entries.append(entry)
        self.root.mainloop()

    def OnValidate(self, P, W):
        # %P = value of the entry if the edit is allowed
        # %W = the tk name of the widget (pathname)
        print("OnValidate:")
        print("P='%s'" % P )
        print("W='%s'" % W )
        self.floatstr_to_float(P, W)
        # return True to display inserted character, validation is done by a re in 'floatstr_to_float()'
        return True

    def floatstr_to_float(self, fs, W):
        preg = re.compile('^\s*(?P<int>\d*)\s*[\.,]?\s*(?P<dec>\d*)\s*$')
        m = preg.match(fs)
        if m:
            print('approved')
            intprt=m.group('int')
            frcprt=m.group('dec')
            f = 0. if (intprt == '' and frcprt == '') else float('%s.%s' %(intprt, frcprt)) # not needed yet
            # currently:    just changing the color of the first entry widget (proof of concept)
            # aim:          pass unique name of edited entry widget to self.change_bg() for changing bg of
            #               appropriate entry widget
            self.change_bg(self.entries[0], 1)
        else:
            print('not approved')
            # see comment in if-statement above
            self.change_bg(self.entries[0], 0)

    def change_bg(self, name, approved):
        if approved == 1:
            name.config(bg=self.default_bg)
        else:
            name.config(bg='#d9534f')

app=MyApp()