Python why is it impossible to enter input in a class ???

Well, already here

 obj = MyClass() 

will not work, because

 def __init__(self, arg): 

those. At least one argument is required. Further, when entering the number we get an error, because there will be a conversion to int, which does not have an isdigit () method - it is a string one and you need to do an inverse transformation (and catching the exception also does not hurt)

and about why it is impossible to output: you don't assign an attribute anywhere, there is no call to self.ipdate_val (x)

on the knee came something like this:

 def recieve_val(self): while True: x = input('Введите количество клеток в квадрате ') str_x = str(x) self.ipdate_val(x) if x == 'stop': break elif not str_x.isdigit(): print ('вы ввели не число ' * 3 ) else: num = int(x) if num < 40: print ('слишком маленкое число') else: summaMassiv1 = int(num) * int(num) print ( summaMassiv1 ) print ( summaMassiv1 ) break # обрывает действие цикла True