Python Coding Interview Questions and Answers for 2 years experience

1. What is Python and why is it popular?

   • Answer: Python is a high-level, general-purpose programming language known for its readability and ease of use. Its popularity stems from its versatility, extensive libraries (like NumPy, Pandas, and Django), large and active community support, and its applicability across various domains like web development, data science, machine learning, and scripting.

2. Explain the difference between lists and tuples in Python.

   • Answer: Both lists and tuples are used to store sequences of items, but lists are mutable (changeable) while tuples are immutable (unchangeable). Lists are defined using square brackets `[]`, while tuples use parentheses `()`. Mutability impacts performance and data integrity; tuples are generally faster and safer for data that shouldn't be modified after creation.

3. What are dictionaries in Python? Give an example.

   • Answer: Dictionaries are unordered collections of key-value pairs. Keys must be immutable (like strings or numbers), while values can be of any data type. They provide fast lookups based on keys. Example: my_dict = {"name": "Alice", "age": 30, "city": "New York"}

4. Explain the concept of inheritance in Python.

   • Answer: Inheritance is a mechanism in object-oriented programming where a class (child class or subclass) inherits attributes and methods from another class (parent class or superclass). This promotes code reusability and establishes an "is-a" relationship between classes. For example, a "Dog" class could inherit from an "Animal" class.

5. What are Python modules and packages?

   • Answer: Modules are files containing Python code (functions, classes, variables). Packages are a way of organizing related modules into a directory hierarchy. They help manage code complexity and reusability. You import modules and packages using the `import` statement.

6. How do you handle exceptions in Python?

   • Answer: Use `try...except` blocks to handle exceptions. The `try` block contains code that might raise an exception, and the `except` block specifies how to handle it. You can specify specific exception types or use a general `except Exception` clause. `finally` blocks execute regardless of whether an exception occurred.

7. Explain the difference between `==` and `is` in Python.

   • Answer: `==` compares the values of two objects, while `is` compares the object identities (memory addresses). `is` checks if two variables refer to the same object in memory. For example, `[1, 2] == [1, 2]` is True, but `[1, 2] is [1, 2]` is usually False because they are different objects in memory.

8. What are list comprehensions? Give an example.

   • Answer: List comprehensions provide a concise way to create lists. They are essentially shorthand for `for` loops. Example: squares = [x**2 for x in range(10)] creates a list of squares from 0 to 9.

9. What are generators in Python?

   • Answer: Generators are a type of iterator that produces values on demand, rather than generating an entire list at once. They use the `yield` keyword instead of `return`. This makes them memory-efficient for processing large datasets.

10. Explain the concept of decorators in Python.

    • Answer: Decorators are a powerful feature that allows you to modify or enhance functions and methods in a clean and readable way. They use the `@` symbol and are essentially functions that take another function as input and return a modified version.

11. What is the Global Interpreter Lock (GIL) in Python?

    • Answer: The GIL is a mechanism in CPython (the standard Python implementation) that allows only one native thread to hold control of the Python interpreter at any one time. This limits true parallelism in multi-threaded applications, though multiprocessing can bypass this limitation.

12. Explain how to use the `map` function in Python.

    • Answer: The `map` function applies a given function to each item of an iterable (like a list) and returns an iterator with the results. Example: `list(map(lambda x: x*2, [1,2,3]))` would return `[2, 4, 6]`.

13. What is the purpose of the `__init__` method in a class?

    • Answer: The `__init__` method is a constructor in Python classes. It's automatically called when you create an instance of the class, and it's used to initialize the object's attributes.

14. How do you create and use a class in Python?

    • Answer: Classes are defined using the `class` keyword followed by the class name and a colon. Methods are defined within the class. Instances are created using the class name followed by parentheses.

15. What is polymorphism in Python?

    • Answer: Polymorphism allows objects of different classes to be treated as objects of a common type. This often involves method overriding, where a subclass provides a specific implementation for a method inherited from a superclass.

16. Explain how to use file handling in Python.

    • Answer: Python uses the built-in `open()` function to work with files. You specify the file path and mode (e.g., 'r' for reading, 'w' for writing). Use methods like `read()`, `write()`, and `close()` to interact with the file.

17. What are lambda functions in Python?

    • Answer: Lambda functions are small, anonymous functions defined using the `lambda` keyword. They are often used for short, simple operations that don't require a full function definition.

18. How do you work with databases in Python? Mention any libraries.

    • Answer: Libraries like `sqlite3` (for SQLite), `psycopg2` (for PostgreSQL), and `MySQLdb` (for MySQL) are commonly used to interact with databases. They provide functions for connecting, querying, and updating data.

19. Explain the concept of iterators in Python.

    • Answer: Iterators are objects that allow you to traverse through a sequence of data one element at a time. They implement the `__iter__` and `__next__` methods. This allows for efficient processing of large datasets.

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