Exercise 10-15:
Modify the UniqueList class to override the UserList.extend method.
extend works like append but takes a list as a parameter. Check the type of each element in the list before adding it.
Answer:
##############################################################################
# Python From Scratch
# Author: Nilo Ney Coutinho Menezes
# Editora Novatec (c) 2010-2025 - LogiKraft 2025
# Site: https://pythonfromscratch.com
# ISBN: 978-85-7522-949-1 (Paperback), 978-85-7522-950-7 (hardcover), 978-85-7522-951-4 (ebook)
#
# File: chapter 10/exercise-10-15.py.py
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from collections import UserList
class UniqueList(UserList):
def __init__(self, elem_class, enumerable=None):
super().__init__(enumerable)
self.elem_class = elem_class
def append(self, elem):
self.check_type(elem)
if elem not in self.data:
super().append(elem)
def extend(self, iterable):
for elem in iterable:
self.append(elem)
def __setitem__(self, position, elem):
self.check_type(elem)
if elem not in self.data:
super().__setitem__(position, elem)
def check_type(self, elem):
if not isinstance(elem, self.elem_class):
raise TypeError("Invalid type")