1. What is Python?

Python is a high-level, interpreted, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Its language constructs as well as its object-oriented approach aim to help programmers write clear, logical code for small and large-scale projects.

2. What are the key features of Python?

Interpreted
Dynamically Typed
Object-Oriented
Cross-Platform
Extensive Standard Library
Strong Community and Ecosystem

3. What is the difference between Python 2 and Python 3?

The major differences include print being a function in Python 3 (print(...)), integer division behaving differently, and strings being Unicode by default.

4. What is a "PEP" in Python?

Python Enhancement Proposal. PEPs are the primary mechanism for proposing new features, collecting community input on an issue, and documenting Python's design decisions.

5. What is "PEP 8"?

The official style guide for Python code, providing recommendations on how to format code for maximum readability.

6. What are the different built-in data types in Python?

Numeric: int, float, complex.
Sequence: list, tuple, range.
Text: str.
Mapping: dict.
Set: set, frozenset.
Boolean: bool.
Binary: bytes, bytearray, memoryview.

7. What is the difference between a "List" and a "Tuple"?

List: Mutable (can be changed); defined with [].
Tuple: Immutable (cannot be changed); defined with ().

8. What is a "Dictionary" in Python?

A mutable collection of key-value pairs where each key must be unique and hashable.

9. What is a "Set" and what makes it unique?

A collection of unique items that is unordered and unindexed. Sets are used to store unique values and perform mathematical operations like union, intersection, and difference.

10. What is "List Comprehension"?

A concise way to create lists using a single line of code (e.g., [x for x in range(10) if x % 2 == 0]).

11. What is "Dictionary Comprehension"?

A concise way to create dictionaries (e.g., {x: x**2 for x in range(5)}).

12. What is "Set Comprehension"?

A concise way to create sets (e.g., {x for x in 'apple'}).

13. What is "Slicing" in Python?

A mechanism to extract specific portions of a sequence (like a list or string) using the [start:stop:step] syntax.

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

is: Checks for identity (if two variables point to the same object in memory).
==: Checks for equality (if the values of two variables are the same).

15. What is the "GIL" (Global Interpreter Lock)?

A mutex that protects access to Python objects, preventing multiple threads from executing Python bytecodes at once. This limits Python's true parallelism on multi-core systems.

16. What is the difference between "Shallow Copy" and "Deep Copy"?

Shallow: Copies the top-level structure; nested objects are still SHARED.
Deep: Recursively copies all objects, creating completely independent copies.

17. What is a "Closure" in Python?

A function that remembers values from its enclosing lexical scope even after the outer function has finished executing.

18. What is a "Decorator"?

A design pattern used to modify or extend the behavior of functions or classes without changing their source code. Use the @ symbol at the top of the function definition.

19. What is a "Generator" and what is the `yield` keyword?

Generators are functions that return an iterator that yields one value at a time using the yield keyword. They are memory-efficient because they generate values on the fly.

20. What is the difference between `Generator Expression` and `List Comprehension`?

List Comprehension: Creates the entire list in memory.
Generator Expression: Returns a generator object that produces items as needed (saves memory).

21. What is the purpose of `*args` and `**kwargs`?

*args: Allows a function to accept any number of positional arguments.
**kwargs: Allows a function to accept any number of keyword arguments (passed as a dictionary).

22. What is "Monkey Patching"?

The practice of changing the behavior of a module, class, or function at runtime.

23. What is "Duck Typing"?

A concept where the type or class of an object is less important than the methods it defines. If it looks like a duck and quacks like a duck, it's treated like a duck.

24. What is the difference between `iter()` and `next()`?

iter(): Used to get an iterator from an object.
next(): Used to retrieve the next item from an iterator.

25. What is the "MRO" (Method Resolution Order)?

The order in which Python looks for methods in a multi-class hierarchy (computed using the C3 Linearization algorithm).

26. What is the difference between a "Class Method" and a "Static Method"?

@classmethod: Receives the class (cls) as the first argument; can access class-level state.
@staticmethod: Receives no special first argument; behaves like a regular function attached to a class.

27. What is "Namespace" in Python?

A mapping from names to objects. Namespaces are created for different levels (e.g., local, global, built-in) to avoid name collisions.

28. What is "Scope" in Python?

The region of a program where a namespace is accessible (Local, Enclosing, Global, Built-in - LEGB rule).

29. What is the purpose of the `nonlocal` and `global` keywords?

global: Used to modify variables in the global scope from within a function.
nonlocal: Used to modify variables in the ближайший enclosing scope (but not global).

30. What is "Self" in Python?

An instance of the class that is used to access its attributes and methods. It is conventions to pass it as the first argument to instance methods.

31. What is the purpose of `init` and `new`?

__new__: Creates the object; called before __init__.
__init__: Initializes the object once it's created.

32. What is the difference between `str` and `repr`?

__str__: Returns a string representation for end-users.
__repr__: Returns an unambiguous string representation for developers (often used in debugging).

33. What is "Pickling" and "Unpickling"?

The process of serializing and deserializing Python objects using the pickle module.

34. What is the purpose of the `with` statement?

It's used for resource management (e.g., opening files, database connections), ensuring that resources are properly cleaned up even if an error occurs.

35. What is the difference between `range()` and `xrange()`?

In Python 2, range() returns a list and xrange() an iterator. In Python 3, range() behaves like xrange().

36. What is the "Pythonic" way of writing code?

Following the principles set forth in the "Zen of Python" (PEP 20), which emphasizes simplicity, readability, and explicitness.

37. What is "Exception Handling" in Python?

Using try, except, else, and finally blocks to manage errors gracefully.

38. What is the difference between `raise` and `assert`?

raise: Manually triggers an exception.
assert: Checks a condition; if false, it raises an AssertionError. It's often used for debugging.

39. What is "Virtual Environment" in Python?

A tool used to create isolated Python environments for each project to avoid version conflicts between dependencies.

40. What is `pip`?

The standard package manager for Python, used to install and manage third-party libraries from the Python Package Index (PyPI).

41. What is the purpose of the `name == "main"` block?

It ensures that the code inside it is only executed if the script is run directly, not if it's imported as a module in another script.

42. What is the "Itertools" module?

A built-in module that provides a set of fast, memory-efficient tools for working with iterators (e.g., count, cycle, combinations).

43. What is the "Collections" module?

A built-in module that provides specialized container data types beyond the built-in ones (e.g., Counter, deque, namedtuple).

44. What is "Metaclass"?

A class of a class. It defines how a class should behave. By default, type is the metaclass in Python.

45. What is the difference between "Abstract Base Class" (ABC) and "Interface"?

Python doesn't have an explicit interface keyword; it uses ABCs (via the abc module) to define a common interface that subclasses must implement.

46. What is the "Property Decorator" (`@property`)?

A built-in way to use getters and setters for class attributes in a clean, Pythonic way.

47. What is the purpose of the `inspect` module?

Used for examining live objects (modules, classes, methods, functions, etc.) and their source code.

48. What is "Type Hinting"?

A way to provide information about the expected types of variables and function arguments/returns (PEP 484), improving code readability and IDE support.

49. What is "Asynchronous Programming" in Python (`asyncio`)?

Using async and await keywords to write concurrent code that can handle many I/O-bound tasks more efficiently than multithreading.

50. What is "Memory Management" in Python?

Python uses reference counting and a cyclic garbage collector to automatically manage memory used by objects.

Python Interview Questions

Table of Contents

What is Python?

What are the key features of Python?

What is the difference between Python 2 and Python 3?

What is a "PEP" in Python?

What is "PEP 8"?

What are the different built-in data types in Python?

What is the difference between a "List" and a "Tuple"?

What is a "Dictionary" in Python?

What is a "Set" and what makes it unique?

What is "List Comprehension"?

What is "Dictionary Comprehension"?

What is "Set Comprehension"?

What is "Slicing" in Python?

What is the difference between <code>is</code> and <code>==</code>?

What is the "GIL" (Global Interpreter Lock)?

What is the difference between "Shallow Copy" and "Deep Copy"?

What is a "Closure" in Python?

What is a "Decorator"?

What is a "Generator" and what is the <code>yield</code> keyword?

What is the difference between <code>Generator Expression</code> and <code>List Comprehension</code>?

What is the purpose of <code>*args</code> and <code>**kwargs</code>?

What is "Monkey Patching"?

What is "Duck Typing"?

What is the difference between <code>iter()</code> and <code>next()</code>?

What is the "MRO" (Method Resolution Order)?

What is the difference between a "Class Method" and a "Static Method"?

What is "Namespace" in Python?

What is "Scope" in Python?

What is the purpose of the <code>nonlocal</code> and <code>global</code> keywords?

What is "Self" in Python?

What is the purpose of <code>__init__</code> and <code>__new__</code>?

What is the difference between <code>__str__</code> and <code>__repr__</code>?

What is "Pickling" and "Unpickling"?

What is the purpose of the <code>with</code> statement?

What is the difference between <code>range()</code> and <code>xrange()</code>?

What is the "Pythonic" way of writing code?

What is "Exception Handling" in Python?

What is the difference between <code>raise</code> and <code>assert</code>?

What is "Virtual Environment" in Python?

What is <code>pip</code>?

What is the purpose of the <code>__name__ == "__main__"</code> block?

What is the "Itertools" module?

What is the "Collections" module?

What is "Metaclass"?

What is the difference between "Abstract Base Class" (ABC) and "Interface"?

What is the "Property Decorator" (<code>@property</code>)?

What is the purpose of the <code>inspect</code> module?

What is "Type Hinting"?

What is "Asynchronous Programming" in Python (<code>asyncio</code>)?

What is "Memory Management" in Python?

What is the purpose of <code>init</code> and <code>new</code>?

What is the difference between <code>str</code> and <code>repr</code>?

What is the purpose of the <code>name == "main"</code> block?