import tkinter as tk

#

# https://stackoverflow.com/questions/4140437/interactively-validating-entry-widget-content-in-tkinter/4140988#4140988

#

def convert(text):

parts = []

while text:

parts.insert(0, text[-3:])

text = text[:-3]

return '.'.join(parts)

def check(d, i, P, s, S, v, V, W):

print("d='%s'" % d)

print("i='%s'" % i)

print("P='%s'" % P)

print("s='%s'" % s)

print("S='%s'" % S)

print("v='%s'" % v)

print("V='%s'" % V)

print("W='%s'" % W)

print('-----')

if V == 'focusin':

print('if focus in')

text = P

# remove points of hundreds

text = text.replace('.', '')

e.delete('0', 'end')

e.insert('end', text)

return True

if V == 'focusout':

print('if focus out')

text = P

# add points of hundreds

parts = text.split(',')

if len(parts) > 0:

parts[0] = convert(parts[0])

text = ','.join(parts)

#e.delete('0', 'end')

#e.insert('end', text)

return True

if V == 'key':

print('if key')

text = P

# validate

parts = text.split(',')

parts_number = len(parts)

if parts_number > 2:

print('too much dots')

return False

if parts_number > 1 and parts[1]: # don't check empty string

if not parts[1].isdecimal() or len(parts[1]) > 2:

print('wrong second part')

return False

if parts_number > 0 and parts[0]: # don't check empty string

if not parts[0].isdecimal() or len(parts[0]) > 8:

print('wrong first part')

return False

return True

# --- main ---

root = tk.Tk()

vcmd = (root.register(check), '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')

e = tk.Entry(root, validate='all', validatecommand=vcmd)

e.pack()

b = tk.Button(root, text='Other widget to set focus')

b.pack()

root.mainloop()