Recap - Custom List
Part of the Object Oriented Programming section of Coddy's Python journey — lesson 36 of 64.
Challenge
MediumIn this challenge, you'll implement a fully functional CustomList class that mimics Python's built-in list behavior while demonstrating your understanding of special methods.
Edit only the customlist.py file following the TODO comments that guide your implementation step-by-step.
Your implementation should support:
- Initialization with optional items
- Indexing (getting/setting values)
- Length checking with
len() - Addition with other lists
- String representation
- Iteration and contains checks
- Methods:
append,pop, andclear
Cheat sheet
A CustomList class can be implemented using special methods (dunder methods) to mimic Python's built-in list behavior:
__init__(self, items=None)- Initialize with optional items__getitem__(self, index)- Enable indexing to get values__setitem__(self, index, value)- Enable indexing to set values__len__(self)- Enablelen()function__add__(self, other)- Enable addition with other lists__str__(self)- String representation__iter__(self)- Enable iteration__contains__(self, item)- Enableinoperator
Common list methods to implement:
append(self, item)- Add item to endpop(self, index=-1)- Remove and return item at indexclear(self)- Remove all items
Try it yourself
from customlist import CustomList
def test_basic_functionality():
"""Test basic CustomList functionality"""
try:
# Test initialization
empty_list = CustomList()
assert len(empty_list) == 0, f"Empty list should have length 0, but has {len(empty_list)}"
init_list = CustomList([1, 2, 3])
assert len(init_list) == 3, f"Initialized list should have length 3, but has {len(init_list)}"
# Test indexing
assert init_list[0] == 1, f"First element should be 1, but got {init_list[0]}"
init_list[1] = 10
assert init_list[1] == 10, f"Element after assignment should be 10, but got {init_list[1]}"
# Test string representation
assert str(init_list) == "[1, 10, 3]", f"String representation incorrect, got {str(init_list)}"
# Test addition
combined = init_list + CustomList([4, 5])
assert len(combined) == 5, f"Combined list should have length 5, but has {len(combined)}"
assert combined[3] == 4, f"Fourth element of combined list should be 4, but got {combined[3]}"
# Test iteration and contains
items = []
for item in combined:
items.append(item)
assert items == [1, 10, 3, 4, 5], f"Iteration produced incorrect items: {items}"
assert 10 in combined, "10 should be in the list"
assert 7 not in combined, "7 should not be in the list"
# Test append and pop
combined.append(6)
assert len(combined) == 6, f"After append, length should be 6, but got {len(combined)}"
assert combined[5] == 6, f"Last element after append should be 6, but got {combined[5]}"
popped = combined.pop()
assert popped == 6, f"Popped value should be 6, but got {popped}"
assert len(combined) == 5, f"After pop, length should be 5, but got {len(combined)}"
# Test clear
combined.clear()
assert len(combined) == 0, f"After clear, length should be 0, but got {len(combined)}"
print("Basic functionality tests passed!")
return True
except Exception as e:
print(f"Basic functionality test failed: {e}")
return False
def test_edge_cases():
"""Test edge cases and boundary conditions"""
try:
# Test with empty list operations
empty_list = CustomList()
# Test pop on empty list
try:
empty_list.pop()
assert False, "pop() on empty list should raise IndexError"
except IndexError:
pass # Expected behavior
# Test indexing on empty list
try:
value = empty_list[0]
assert False, "Indexing empty list should raise IndexError"
except IndexError:
pass # Expected behavior
# Test with None values
none_list = CustomList([None, None])
assert len(none_list) == 2, f"List with None values should have length 2, got {len(none_list)}"
assert none_list[0] is None, "First element should be None"
# Test with mixed types
mixed_list = CustomList([1, "string", 3.14, [1, 2], {"key": "value"}])
assert len(mixed_list) == 5, f"Mixed type list should have length 5, got {len(mixed_list)}"
assert mixed_list[1] == "string", f"Second element should be 'string', got {mixed_list[1]}"
# Test adding with regular list
result = mixed_list + [6, 7, 8]
assert len(result) == 8, f"After adding regular list, length should be 8, got {len(result)}"
assert result[5] == 6, f"Sixth element should be 6, got {result[5]}"
# Test adding with empty list
result = mixed_list + []
assert len(result) == 5, f"After adding empty list, length should be 5, got {len(result)}"
assert result[0] == 1, f"First element should still be 1, got {result[0]}"
# Test repr
repr_str = repr(CustomList([1, 2, 3]))
assert repr_str == "CustomList([1, 2, 3])", f"repr should be 'CustomList([1, 2, 3])', got {repr_str}"
print("Edge case tests passed!")
return True
except Exception as e:
print(f"Edge case test failed: {e}")
return False
def test_large_lists():
"""Test performance with large lists"""
try:
# Create and test operations on large lists
# Create a large list
large_list = CustomList(range(10000))
assert len(large_list) == 10000, f"Large list should have length 10000, got {len(large_list)}"
# Test indexing on large list
assert large_list[9999] == 9999, f"Last element should be 9999, got {large_list[9999]}"
# Test contains on large list
assert 5000 in large_list, "5000 should be in the large list"
assert 10001 not in large_list, "10001 should not be in the large list"
# Test addition of two large lists
other_large = CustomList(range(10000, 20000))
combined = large_list + other_large
assert len(combined) == 20000, f"Combined large lists should have length 20000, got {len(combined)}"
assert combined[0] == 0, f"First element should be 0, got {combined[0]}"
assert combined[19999] == 19999, f"Last element should be 19999, got {combined[19999]}"
print("Large list tests passed!")
return True
except Exception as e:
print(f"Large list test failed: {e}")
return False
def test_nested_lists():
"""Test with nested CustomList objects"""
try:
# Test nested CustomList objects
inner1 = CustomList([1, 2, 3])
inner2 = CustomList([4, 5, 6])
outer = CustomList([inner1, inner2, 7])
assert len(outer) == 3, f"Outer list should have length 3, got {len(outer)}"
assert outer[0] is inner1, "First element should be inner1"
assert len(outer[0]) == 3, f"First inner list should have length 3, got {len(outer[0])}"
assert outer[0][1] == 2, f"Second element of first inner list should be 2, got {outer[0][1]}"
# Test modifying inner list
inner1.append(4)
assert len(outer[0]) == 4, f"After append, inner list should have length 4, got {len(outer[0])}"
assert outer[0][3] == 4, f"Fourth element of inner list should be 4, got {outer[0][3]}"
# Test nested addition
result = outer[0] + outer[1]
assert len(result) == 7, f"Combined inner lists should have length 7, got {len(result)}"
assert result[0] == 1, f"First element should be 1, got {result[0]}"
assert result[6] == 6, f"Last element should be 6, got {result[6]}"
print("Nested list tests passed!")
return True
except Exception as e:
print(f"Nested list test failed: {e}")
return False
def test_custom_operations():
"""Test custom operations and combinations"""
try:
# Test custom operations and method combinations
# Test chained operations
list1 = CustomList([1, 2])
list2 = CustomList([3, 4])
list3 = CustomList([5, 6])
# Chain additions
result = list1 + list2 + list3
assert len(result) == 6, f"Chained addition should have length 6, got {len(result)}"
assert result[5] == 6, f"Last element should be 6, got {result[5]}"
# Test append and pop sequence
test_list = CustomList([1, 2, 3])
test_list.append(4)
test_list.append(5)
assert test_list.pop() == 5, "First pop should return 5"
assert test_list.pop() == 4, "Second pop should return 4"
assert len(test_list) == 3, f"After two pops, length should be 3, got {len(test_list)}"
# Test clear and then append
test_list.clear()
assert len(test_list) == 0, f"After clear, length should be 0, got {len(test_list)}"
test_list.append(10)
assert len(test_list) == 1, f"After append to cleared list, length should be 1, got {len(test_list)}"
assert test_list[0] == 10, f"Element should be 10, got {test_list[0]}"
# Test adding empty lists
empty1 = CustomList()
empty2 = CustomList()
empty_sum = empty1 + empty2
assert len(empty_sum) == 0, f"Sum of empty lists should be empty, got length {len(empty_sum)}"
print("Custom operations tests passed!")
return True
except Exception as e:
print(f"Custom operations test failed: {e}")
return False
# Run the selected test or all tests
test_case = input()
if test_case == "basic":
test_basic_functionality()
elif test_case == "edge":
test_edge_cases()
elif test_case == "large":
test_large_lists()
elif test_case == "nested":
test_nested_lists()
elif test_case == "custom":
test_custom_operations()
else:
print("Invalid test case. Running basic tests by default.")
test_basic_functionality()All lessons in Object Oriented Programming
1Fundamentals of OOP
External FilesIntroduction to OOPClasses vs ObjectsThe self ParameterMethodsAttributesConstructor Method (__init__)Recap - Simple Calculator4Inheritance
Basic InheritanceThe super() FunctionMethod OverridingMultiple InheritanceMethod Resolution OrderRecap - Employee Hierarchy7Special Methods
Magic Methods IntroductionOperator OverloadingContainer Magic MethodsRecap - Custom List10Design Patterns Part 1
Intro to design patternSingleton PatternFactory PatternObserver PatternStrategy Pattern2Decorators
Introduction to DecoratorsProperty DecoratorStatic Method DecoratorClass Method Decorator5Polymorphism
Method Overriding RevisitedDuck TypingAbstract Classes and MethodsInterface DesignRecap - Shape Calculator8Advanced OOP Concepts
Composition vs InheritanceMixinsStatic and Class MethodsClass DecoratorsContext Managers3Class Properties
Instance vs Class VariablesProperty DecoratorsPrivate AttributesRecap - Bank Account Manager6Encapsulation
Public, Protected, Private MemAccess ModifiersInformation HidingProperty Decorators AdvancedRecap - Student Records System12Project: Library Management
Project OverviewBook and User Classes