Python interview questions and answers
Basic Python Questions
What is Python?
Python is a high-level, interpreted programming language known for its readability and versatility.
What are the key features of Python?
Easy to learn, dynamically typed, interpreted, extensive libraries, and support for multiple programming paradigms.
What is PEP 8?
PEP 8 is the style guide for Python code, outlining conventions for writing clean and readable code.
How do you declare a variable in Python?
Simply assign a value to a variable name, e.g., x = 10.
What are lists in Python?
Lists are ordered, mutable collections that can hold mixed data types, e.g., my_list = [1, 'hello', 3.14].
How do you create a function in Python?
Use the def keyword, e.g.:
python
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def my_function():
return "Hello, World!"
What is a dictionary in Python?
A dictionary is an unordered collection of key-value pairs, e.g., my_dict = {'name': 'Alice', 'age': 25}.
How do you handle exceptions in Python?
Use try and except blocks:
python
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try:
x = 1 / 0
except ZeroDivisionError:
print("Division by zero!")
What are tuples?
Tuples are immutable, ordered collections, e.g., my_tuple = (1, 2, 3).
What are sets in Python?
Sets are unordered collections of unique elements, e.g., my_set = {1, 2, 3}.
Intermediate Python Questions
What is a lambda function?
A small anonymous function defined with the lambda keyword, e.g., add = lambda x, y: x + y.
What is the difference between append() and extend()?
append() adds a single element, while extend() adds multiple elements to a list.
How do you read and write files in Python?
Use the open() function:
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with open('file.txt', 'r') as f:
data = f.read()
What are list comprehensions?
A concise way to create lists, e.g., [x**2 for x in range(10)].
What is the purpose of the self keyword?
self refers to the instance of the class in methods.
What is a module in Python?
A module is a file containing Python code (functions, classes) that can be imported.
What is the difference between == and is?
== checks for value equality, while is checks for object identity.
What is a decorator?
A decorator is a function that modifies the behavior of another function.
What is a generator?
A generator is an iterable that produces items one at a time using yield.
What are Python's built-in data types?
int, float, str, list, tuple, dict, set, bool.
Advanced Python Questions
What is multithreading in Python?
A technique where multiple threads run concurrently to perform tasks in parallel.
What is the Global Interpreter Lock (GIL)?
A mutex that protects access to Python objects, preventing multiple native threads from executing Python bytecodes simultaneously.
How do you create a class in Python?
Use the class keyword:
python
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class MyClass:
def __init__(self):
self.value = 0
What is inheritance in Python?
A mechanism where a new class derives from an existing class, inheriting its attributes and methods.
What is polymorphism?
The ability to present the same interface for different data types, e.g., method overriding.
What is an abstract class?
A class that cannot be instantiated and typically includes abstract methods that must be implemented by subclasses.
What are *args and **kwargs?
*args allows passing a variable number of non-keyword arguments, and **kwargs allows passing a variable number of keyword arguments.
What is the difference between deep copy and shallow copy?
A shallow copy creates a new object but inserts references into it, while a deep copy creates a new object and recursively copies all objects.
What is a context manager?
A construct that allows setup and teardown actions when working with resources, typically using the with statement.
What is the purpose of the pass statement?
pass is a null statement used as a placeholder where syntactically required but no action is needed.
Data Structures and Algorithms
What is a stack?
A collection of elements with last-in-first-out (LIFO) access.
What is a queue?
A collection of elements with first-in-first-out (FIFO) access.
What are linked lists?
A data structure where each element points to the next, allowing for efficient insertions and deletions.
What is a binary tree?
A tree data structure where each node has at most two children.
What is a hash table?
A data structure that implements an associative array, mapping keys to values for fast lookup.
How do you sort a list in Python?
Use the sort() method or the sorted() function.
What is the time complexity of searching in a binary search tree?
O(log n) on average; O(n) in the worst case.
What is a breadth-first search (BFS)?
An algorithm for traversing or searching tree/graph data structures, exploring neighbors before going deeper.
What is a depth-first search (DFS)?
An algorithm for traversing or searching tree/graph data structures, exploring as far down a branch as possible before backtracking.
What is dynamic programming?
A method for solving complex problems by breaking them down into simpler subproblems and storing their solutions.
Libraries and Frameworks
What is NumPy?
A library for numerical computing in Python, providing support for large multi-dimensional arrays and matrices.
What is Pandas?
A data manipulation and analysis library offering data structures like DataFrames.
What is Matplotlib?
A plotting library for creating static, animated, and interactive visualizations in Python.
What is Flask?
A lightweight web framework for building web applications in Python.
What is Django?
A high-level web framework that encourages rapid development and clean, pragmatic design.
What is TensorFlow?
An open-source library for numerical computation and machine learning.
What is Keras?
A high-level neural networks API, written in Python, that runs on top of TensorFlow.
What is Scikit-learn?
A machine learning library that provides simple and efficient tools for data mining and data analysis.
What is Beautiful Soup?
A library for parsing HTML and XML documents, used for web scraping.
What is Requests?
A simple library for making HTTP requests in Python.
Miscellaneous
What is the difference between Python 2 and Python 3?
Python 3 has better support for Unicode, improved syntax, and is the current version; Python 2 is no longer maintained.
What is the use of the __init__ method?
It initializes the object's state when an instance of a class is created.
What is the __str__ method?
It defines a string representation of an object, used by the print() function.
What is the __repr__ method?
It defines an unambiguous string representation of an object, useful for debugging.
How do you manage dependencies in Python?
Use a requirements.txt file or a virtual environment with venv or conda.
What are f-strings?
Formatted string literals introduced in Python 3.6, allowing for easy string interpolation, e.g., f"Hello, {name}!".
What is the map() function?
It applies a function to all items in an input list (or iterable) and returns a map object.
What is the filter() function?
It filters items out of an iterable based on a function that returns True or False.
What is the reduce() function?
It applies a rolling computation to sequential pairs of values in a list.
What is the purpose of the with statement?
It simplifies exception handling by encapsulating common preparation and cleanup tasks.
Testing and Debugging
What is unit testing?
A software testing method where individual units of code are tested for correctness.
What is the unittest module?
A built-in Python module for creating and running unit tests.
How do you run tests with unittest?
Use the command line to run the test file, or include if __name__ == "__main__": unittest.main().
What is pytest?
A third-party testing framework that provides a more powerful testing environment than unittest.
What is a mock object?
An object that simulates the behavior of real objects in controlled ways, used for testing.
What are assertions in Python?
Statements that check if a condition is True, raising an AssertionError if not.
How can you debug a Python program?
Use print statements, logging, or a debugger like pdb.
What is the purpose of logging?
To track events that happen during execution, useful for debugging and monitoring.
What is the difference between print() and logging?
print() outputs to the console, while logging can be configured to output to various destinations and levels of severity.
What is continuous integration?
A practice where developers regularly integrate code changes into a shared repository, followed by automated testing.
Miscellaneous Concepts
What is the difference between an iterable and an iterator?
An iterable can return an iterator using iter(), while an iterator is an object with a __next__() method.
What is monkey patching?
Dynamically modifying or extending a class or module at runtime.
What is the purpose of the __slots__ declaration?
To restrict attribute creation on instances of a class, saving memory.
What are context variables?
Variables that maintain state across asynchronous tasks or threads.
What is the use of the async and await keywords?
They are used to define asynchronous functions and wait for asynchronous operations to complete.
What is the purpose of the yield keyword?
It turns a function into a generator, allowing it to return values one at a time.
What is the difference between isinstance() and type()?
isinstance() checks if an object is an instance of a class or a tuple of classes, while type() returns the object's type.
What is type hinting?
A way to indicate the expected data types of function parameters and return values, improving code readability and type checking.
What is the purpose of the not operator?
It negates a Boolean expression, returning True if the expression is False and vice versa.
What is a binary search?
An efficient algorithm for finding an item in a sorted list by repeatedly dividing the search interval in half.
How can you reverse a string in Python?
Use slicing: reversed_string = my_string[::-1].
What is the purpose of the import statement?
To include modules and their functions, classes, or variables in your code.
How do you check if a key exists in a dictionary?
Use the in operator, e.g., if key in my_dict:.
What is the difference between shallow and deep copies?
A shallow copy duplicates the outer object, but references nested objects, while a deep copy duplicates all objects recursively.
How do you create a virtual environment?
Use python -m venv myenv to create a virtual environment named myenv.
What is the super() function?
It returns a temporary object of the superclass, allowing access to its methods.
What are dataclasses?
A decorator that automatically generates special methods like __init__() and __repr__() for classes.
What is asyncio?
A library to write concurrent code using the async/await syntax, useful for I/O-bound tasks.
How do you convert a string to a list?
Use the split() method, e.g., my_list = my_string.split().
What is the purpose of the __call__ method?
It allows an instance of a class to be called as a function.
What is a callback function?
A function passed into another function as an argument, executed at a certain point.
What is a function closure?
A function that captures the local variables of its enclosing scope.
How do you check if a string contains a substring?
Use the in operator, e.g., if "substring" in my_string:.
What are environment variables?
Variables outside the program that influence its behavior, often used for configuration.
What is the difference between a class and a module?
A class is a blueprint for creating objects, while a module is a file containing Python code that can include classes, functions, and variables.
What is a property in Python?
A built-in decorator for defining methods in a class that can be accessed like attributes.
What are namedtuples?
A subclass of tuples with named fields, allowing for more readable code.
What is the json module used for?
For parsing JSON data and converting Python objects to JSON format.
What is a deque?
A double-ended queue from the collections module that allows fast appends and pops from both ends.
How do you measure the performance of a piece of code?
Use the time module or the timeit module to benchmark execution time.
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