Default Parameters

Mutable Objects in Python

Mutable objects in Python are objects whose internal state can be changed after they are created. This means you can modify their contents without creating a new object. In contrast, immutable objects cannot be changed after creation; any operation that appears to modify them actually creates a new object.

Key characteristics of mutable objects:

• Modifiable: Their values can be altered in place.
• Methods that change state: They often have methods that modify their contents (e.g., append() for lists, insert() for lists, update() for dictionaries).
• Impact on references: Changes to a mutable object are reflected in all references to that object.

Examples of Mutable Objects:

• Lists:

my_list = 1, 2, 3
my_list.append(4)  # Modifies the original list
print(my_list)  # Output: 1, 2, 3, 4

• Dictionaries:

my_dict = {'a': 1, 'b': 2}
my_dict['c']] = 3  # Modifies the original dictionary
print(my_dict)  # Output: {'a': 1, 'b': 2, 'c': 3}

• Sets:

my_set = {1, 2, 3}
my_set.add(4) # Modifies the original set
print(my_set) # Output: {1, 2, 3, 4}

• Sets in Python (Note: This will be a seperate note)

• User-defined classes (if implemented to be mutable): You can create your own mutable objects by defining classes. The use of instance variables and methods is typically how you will make these modifications

Important Considerations:

• Aliasing: When you assign a mutable object to multiple variables, they all refer to the same object in memory. Changes made through one variable are visible through all others.

list1 = 1, 2, 3
list2 = list1  # list2 is an alias for list1
list1.append(4)
print(list2)  # Output: 1, 2, 3, 4  (list2 is also modified)

• Copying: To avoid unintended side effects from aliasing, you can create a copy of a mutable object using techniques like slicing ([:]]) for lists or the copy() method for more complex objects. See Shallow vs Deep Copying for more details.

Immutable Objects in Python (Note: This will be a seperate note)

Shallow vs Deep Copying (Note: This will be a seperate note)