How do I validate a date string format in python?

I have a python method which accepts a date input as a string.

How do I add a validation to make sure the date string being passed to the method is in the ffg. format:

    'YYYY-MM-DD'

if it's not, method should raise some sort of error

    >>> import datetime
    >>> def validate(date_text):
        try:
            datetime.datetime.strptime(date_text, '%Y-%m-%d')
        except ValueError:
            raise ValueError("Incorrect data format, should be YYYY-MM-DD")


    >>> validate('2003-12-23')
    >>> validate('2003-12-32')

    Traceback (most recent call last):
      File "<pyshell#20>", line 1, in <module>
        validate('2003-12-32')
      File "<pyshell#18>", line 5, in validate
        raise ValueError("Incorrect data format, should be YYYY-MM-DD")
    ValueError: Incorrect data format, should be YYYY-MM-DD

From: stackoverflow.com/q/16870663