অরেঞ্জ রেভুলেশন কোথায় সংঘটিত হয়েছে?

Topic: Python Programming - Data Types & Mutability

Consider the following Python code snippet and determine what output will be generated when executed:

x = [1, 2, 3]
y = x
y.append(4)
print(x)

Choose the correct option:

    
• A) [1, 2, 3]
    
• B) [1, 2, 3, 4]
    
• C) TypeError: list is immutable
    
• D) None

Correct Answer: B) [1, 2, 3, 4]

Explanation:

In Python, lists are mutable objects. When you assign y = x, Python does not create an independent copy of the list. Instead, both x and y point to the exact same list object in memory.

Key breakdown:

    
• Reference Assignment: The assignment y = x creates an alias. Both variables reference the same memory address.
    
• In-place Modification: The append() method mutates the existing list object rather than returning a new list.
    
• Result: Any modification made via y will be reflected when accessing x.

Why the other options are incorrect:

    
• A is incorrect: Modifying y directly impacts x because no copy was made. (To keep x unchanged, you would use y = x.copy() or y = x[:]).
    
• C is incorrect: Lists in Python are mutable by design; tuples are the immutable sequence type.
    
• D is incorrect: Although y.append(4) returns None, the variable x holds the modified list, which is printed.