30 Essential Python Interview Questions: From Beginner to Advanced

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Python Interview Questions:

  1. What is Python, and what are its key features?
    • Python is a high-level, interpreted programming language known for its readability, simplicity, and versatility. Key features include dynamic typing, extensive libraries, and support for multiple programming paradigms.
  2. What is the difference between a list and a tuple in Python?
    • A list is mutable, meaning its contents can be changed, while a tuple is immutable, meaning its contents cannot be altered after creation.
  3. How do you handle exceptions in Python?
    • You can handle exceptions in Python using the try, except, else, and finally blocks to manage errors and perform cleanup operations.
  4. What are Python decorators, and how are they used?
    • Decorators are functions that modify the behavior of other functions or methods. They are often used to add functionality like logging or access control.
  5. What is a Python dictionary, and how does it differ from a list?
    • A dictionary is an unordered collection of key-value pairs, while a list is an ordered collection of items. Dictionaries provide fast access to values based on keys.
  6. What are Python modules, and how do you create one?
    • Modules are Python files that contain reusable code, including functions and classes. You create a module by saving a .py file and importing it into other Python scripts.
  7. What is the purpose of the __init__ method in Python classes?
    • The __init__ method is a constructor that initializes an object’s attributes when an instance of a class is created.
  8. How can you create a virtual environment in Python?
    • You can create a virtual environment using the venv module by running python -m venv env_name, which creates an isolated environment for dependencies.
  9. What is list comprehension in Python?
    • List comprehension is a concise way to create lists by applying an expression to each item in an iterable, often resulting in more readable code.
  10. How do you read and write files in Python?
    • You can read and write files in Python using the open() function with modes like 'r' for reading and 'w' for writing, and then using methods like read(), readlines(), or write().

Intermediate Level:

  1. What is the difference between == and is in Python?
    • The == operator checks for value equality, while the is operator checks for identity, meaning it verifies whether two variables point to the same object in memory.
  2. What are Python generators, and how do they differ from regular functions?
    • Generators are special functions that yield values one at a time and maintain their state between calls, allowing for lazy evaluation and memory efficiency.
  3. How do you perform unit testing in Python?
    • You can perform unit testing in Python using the unittest module, which provides a framework for creating and running tests.
  4. What is the Global Interpreter Lock (GIL) in Python?
    • The GIL is a mutex that protects access to Python objects, preventing multiple native threads from executing Python bytecode simultaneously, which can affect multithreading performance.
  5. How can you improve the performance of a Python application?
    • You can improve performance by optimizing algorithms, using built-in functions, leveraging libraries like NumPy for numerical operations, and using tools like Cython or PyPy for compilation.
  6. What are Python’s built-in data types?
    • Python’s built-in data types include integers, floats, strings, lists, tuples, dictionaries, sets, and booleans.
  7. What is a lambda function in Python?
    • A lambda function is an anonymous, small function defined using the lambda keyword, typically used for short, throwaway functions.
  8. What is the purpose of the self parameter in Python class methods?
    • The self parameter refers to the instance of the class itself, allowing access to instance variables and methods within class methods.
  9. What is the difference between shallow copy and deep copy in Python?
    • A shallow copy creates a new object but inserts references into it to the objects found in the original, while a deep copy creates a new object and recursively copies all objects found in the original.
  10. How do you create a custom exception in Python?
    • You can create a custom exception by defining a new class that inherits from the built-in Exception class and implementing any necessary methods.

Advanced Level:

  1. What is the purpose of the with statement in Python?
    • The with statement simplifies exception handling by encapsulating common preparation and cleanup tasks, ensuring resources are properly managed.
  2. How do you implement inheritance in Python?
    • You implement inheritance in Python by defining a new class that derives from an existing class, allowing the new class to inherit attributes and methods.
  3. What are the differences between Python 2 and Python 3?
    • Key differences include print function syntax, integer division behavior, and the introduction of new features like type hints and f-strings in Python 3.
  4. How can you use Python to interact with databases?
    • You can use Python’s built-in sqlite3 module for SQLite databases or external libraries like SQLAlchemy and psycopg2 for other databases like PostgreSQL.
  5. What is a context manager in Python?
    • A context manager is an object that defines the runtime context to be established when executing a with statement, managing resource allocation and deallocation.
  6. How can you use Python for web scraping?
    • You can use libraries like Beautiful Soup and Scrapy to extract data from web pages and parse HTML/XML content in Python.
  7. What are Python decorators, and how do they work?
    • Python decorators are functions that take another function as an argument and extend or modify its behavior without changing its code.
  8. How do you manage package dependencies in Python?
    • You manage package dependencies using pip and a requirements.txt file, which lists the packages needed for a project.
  9. What is asynchronous programming in Python?
    • Asynchronous programming in Python allows for concurrent execution of code using the asyncio library, enabling tasks to run independently and efficiently.
  10. How can you serialize and deserialize objects in Python?
    • You can serialize objects in Python using the pickle module, which converts Python objects into byte streams, and deserialize them by converting byte streams back into Python objects.

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