How to parse python grab response correctly?

Question

Python

Such a question, I'm trying to make a parser for VKontakte accounts in python (python).
I'm stuck on the function of validating the login:password pair
here is the function

from grab import *

def isValid(login, passw):
    
    grab = Grab(log_file='out.html')
    grab.go("https://vk.com/login")
    grab.set_input("email", login)
    grab.set_input("pass", passw)
    grab.submit()

    #если логин успешный то return 1 иначе return 0

if the login is successful, then my VK page appears in out.html and an indication of my VKontakte ID
Question: how to parse the answer and find out programmatically whether the login was successful or not
All hope is for you)