Core Python Questions

1. What is the difference between a list and a tuple?

Answer:

• Mutability: Lists are mutable (can be changed), tuples are immutable (cannot be changed).
• Syntax: Lists use [], tuples use ().
• Performance: Tuples are slightly faster and consume less memory.
• Use Case: Use lists for collections that change; use tuples for fixed data records.

2. Explain `*args` and `**kwargs`.

Answer:

• *args allows passing a variable number of positional arguments (received as a tuple).
• **kwargs allows passing a variable number of keyword arguments (received as a dictionary).

def func(*args, **kwargs):
    print(args)   # (1, 2)
    print(kwargs) # {'a': 3}

func(1, 2, a=3)

3. How does Python handle memory management?

Answer: Python uses a private heap containing all Python objects and data structures. The management of this private heap is ensured internally by the Python memory manager.

• Reference Counting: The primary mechanism. When an object's reference count drops to zero, it is deallocated.
• Garbage Collector: A cyclic garbage collector handles reference cycles that reference counting cannot catch.

4. What are Python decorators?

Answer: A decorator is a design pattern in Python that allows a user to add new functionality to an existing object without modifying its structure. It is usually a function that takes another function as an argument and extends its behavior.

5. What are Generators and the `yield` keyword?

Answer: Generators are functions that return an iterable set of items, one at a time, in a special way.

• When an iteration over a set of items starts using the for statement, the generator is run.
• Once the generator's function code reaches a yield statement, the generator yields its execution back to the for loop, returning a new value from the set.
• Benefit: Memory efficient. It doesn't store the whole list in memory.

6. Explain Context Managers (`with` statement).

Answer: Context managers allow you to allocate and release resources precisely when you want to. The most widely used example is the with statement.

with open('file.txt', 'w') as f:
    f.write('hello')

It ensures that the file is closed automatically, even if an exception occurs. It uses the __enter__ and __exit__ magic methods.

7. What is the difference between `is` and `==`?

Answer:

• == checks for value equality. (Do these two objects contain the same data?)
• is checks for reference equality. (Do these two variables point to the exact same object in memory?)