How do the methods of passing mutable and immutable data to a function differ?

In Python, mutable and immutable objects are passed to functions by reference, but their behavior when modified inside the function differs.

• Immutable objects (e.g., numbers, strings, tuples) cannot be changed inside the function. If you try to modify them, a new object is created, and the original remains unchanged.

• Mutable objects (e.g., lists, dictionaries, sets) can be modified inside the function, and these changes will be visible outside the function because the reference points to the same object.

Example:

def modify_immutable(x):
    x = x + 1  # creates a new object

num = 10
modify_immutable(num)
print(num)  # Will print 10, original object is unchanged


def modify_mutable(lst):
    lst.append(4)  # modifies the object by reference

my_list = [1, 2, 3]
modify_mutable(my_list)
print(my_list)  # Will print [1, 2, 3, 4], object has changed

Thus, when passing mutable objects, the function can change their state, but when passing immutable objects, it cannot.