[Tkinter] How Does Entry Verification Work?

[deanhystad]

The problem with only calling once appears to be related to returning None. I changed you callback to this and it is called for each keystroke.

def validatePhone(num):
    print('called')
    pattern=re.compile('\d{3}-\d{3}-\d{4}')
    ok =  pattern.search(num)
    print('got here', num, ok)
    return True if ok else False

To verify I tried both of these for validate. Returning None behaves as you saw. Called only once then validation no longer used. Returning False runs each time the key is pressed.

def validateFalse(num):
    print(num)
    return False

def validateNone(num):
    print(num)
    return None

So your validation function needs to return True or False. But you still have a problem. The only way you can enter a phone number is using copy/paste. Typing will never match your pattern because 1 digit does not match your pattern and typing in "555-867-5309" requires you first type "5".

I don't know how to write a regex that would match '5', '55', '555' and '555-' but not '55-', '5-' or '-'. This works.

def validatePhone(num):
    pattern = 'ddd-ddd-dddd'
    if len(num) > len(pattern):
        return False
    for digit, chr in zip(num, pattern):
        if chr == 'd':
            if not digit.isdigit():
               return False
        elif digit != chr:
            return False
    return True