Question 1

What is the difference between append() and extend() on a Python list?

Accepted Answer

append() adds a single element; extend() adds all elements from an iterable. [1,2].append([3,4]) → [1,2,[3,4]] (nested list). [1,2].extend([3,4]) → [1,2,3,4] (elements merged). Use extend() when you want to merge two lists.

Question 2

What is a decorator in Python?

Accepted Answer

A function that wraps another function to extend its behavior without modifying it. Decorators use the @syntax. They take a function, add behavior, and return a new function. Commonly used for logging, authentication, caching, and timing.

Question 3

What does *args do in a Python function definition?

Accepted Answer

Allows the function to accept a variable number of positional arguments as a tuple. *args collects extra positional arguments into a tuple. def f(*args) lets you call f(1,2,3) and inside the function args = (1, 2, 3). **kwargs does the same for keyword arguments.

Question 4

What is the difference between a shallow copy and a deep copy in Python?

Accepted Answer

Shallow copy copies references to nested objects; deep copy creates fully independent copies of nested objects. Shallow copy (copy.copy) copies the outer object but nested objects are still shared. Deep copy (copy.deepcopy) recursively copies everything — changes to the copy never affect the original.

Question 5

What is list comprehension in Python?

Accepted Answer

A concise single-line syntax to create a new list by transforming or filtering an iterable. [x*2 for x in range(5)] creates [0,2,4,6,8] — equivalent to a for loop building a list. It's more readable and often faster than an explicit loop.

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