Python - List - Int List

[sophi]

class IntList(list):
       def __init__(self):
          self.internal_list = []
       def append(self, elem):
           if not isinstance(elem, int):
               raise TypeError('x musi byt typu Integer')
           self.internal_list[len(self.internal_list):] = [elem]
       def getList(self):
           return self.internal_list

I have that, after a long time :D but I don't know if is the right implementation. Maybe I have problem with print some list. Should I add some others methods ?