Top 30 Most Common Python Interview Questions You Should Prepare For
Written by
James Miller, Career Coach
Python is a cornerstone language in the tech industry, powering everything from web development and data science to automation and artificial intelligence. Its readability, extensive libraries, and strong community support make it a popular choice for developers and companies alike. Landing a Python role often requires demonstrating not just coding ability but also a solid understanding of the language's core concepts, data structures, object-oriented principles, and common practices. Preparing for your interview by reviewing frequently asked questions is a crucial step. This guide compiles 30 essential Python interview questions, covering fundamental topics and practical scenarios, to help you build confidence and articulate your knowledge effectively. Whether you're a junior developer or seasoned engineer, revisiting these concepts will sharpen your skills and boost your interview performance. Mastering these questions will showcase your proficiency and readiness to tackle real-world Python development challenges. Prepare to dive deep into Python's intricacies and ace your next technical interview.
What Are Python Interview Questions?
Python interview questions are designed to assess a candidate's proficiency and understanding of the Python programming language. These questions cover a wide range of topics, including core syntax, data types (like lists, tuples, dictionaries, sets), control flow (loops, conditionals), functions, object-oriented programming (classes, inheritance, polymorphism), error handling, modules, memory management, and common libraries. Interviewers use these questions to gauge a candidate's theoretical knowledge, problem-solving skills using Python, and ability to write clean, efficient, and idiomatic Python code. They often start with fundamental concepts and progressively move towards more complex topics or scenario-based questions to evaluate depth of understanding and practical experience. Preparing for these questions involves reviewing Python's features, practicing coding exercises, and understanding the underlying mechanisms of the language.
Why Do Interviewers Ask Python Interview Questions?
Interviewers ask Python interview questions for several key reasons. Firstly, they need to verify that a candidate possesses the necessary technical skills to perform the job. Python is a versatile language, and questions help determine if the candidate has a strong grasp of its fundamentals and advanced features relevant to the specific role (e.g., web development, data analysis, machine learning). Secondly, these questions reveal a candidate's problem-solving approach and logical thinking. How a candidate breaks down a problem, explains their thought process, and utilizes Python constructs provides insight into their coding style and efficiency. Thirdly, questions about language internals, best practices (like PEP 8), and memory management assess a candidate's depth of knowledge and commitment to writing high-quality, maintainable code. Ultimately, Python interview questions are a critical tool for evaluating a candidate's technical foundation and potential contribution to the team.
What is Python, and list some of its key features?
What are Python lists and tuples?
What is
init()in Python?What is the difference between Python Arrays and Lists?
What is the difference between global and local scope?
What is an iterator in Python?
Which collection does not allow duplicate members?
What is inheritance in Python?
How does Python manage memory? Explain reference counting and garbage collection.
Does Python support multiple inheritance?
Difference between list and tuple?
What is slicing in Python?
How is multithreading achieved in Python?
Which is faster, Python list or NumPy arrays?
What is shallow copy vs deep copy in Python?
What is PEP 8?
What does the
break,continue, andpassstatements do?How to delete a file using Python?
What are Python’s primary built-in data types?
What is the syntax to print the type of a variable?
How are classes created in Python?
What is a Python expression?
What is the difference between
==andisin Python?What is type conversion in Python?
Name some commonly used built-in Python modules.
How can you make a Python script executable on Unix?
What is a lambda function?
What is list comprehension?
Explain the process of compilation and linking in Python.
How to handle exceptions in Python?
Preview List
1. What is Python, and list some of its key features?
Why you might get asked this:
Assess fundamental understanding of Python's identity and capabilities. Checks if you know its core characteristics.
How to answer:
Define Python and list key features concisely. Mention its nature (high-level, interpreted) and strengths (readability, versatility).
Example answer:
Python is a high-level, interpreted, general-purpose language. Key features include readability via clean syntax, dynamic typing, extensive standard libraries, automatic memory management, and support for multiple programming paradigms.
2. What are Python lists and tuples?
Why you might get asked this:
Evaluates knowledge of fundamental sequence data types and their key difference (mutability).
How to answer:
Describe each type, noting what they store (heterogeneous items) and the crucial distinction: lists are mutable, tuples are immutable.
Example answer:
Lists are mutable sequences allowing heterogeneous items, supporting methods like append/remove. Tuples are immutable sequences for heterogeneous items; once created, their contents cannot change.
3. What is init() in Python?
Why you might get asked this:
Tests understanding of object-oriented programming fundamentals, specifically constructors.
How to answer:
Explain its role as a constructor method. Mention it's automatically called upon object creation to initialize attributes.
Example answer:
init() is a special method in Python classes called a constructor. It's automatically invoked when you create a new object instance and is used to initialize the object's attributes.
4. What is the difference between Python Arrays and Lists?
Why you might get asked this:
Checks if you understand the distinction between Python's built-in list and array structures (often from the array module or NumPy).
How to answer:
Highlight that lists are dynamic and heterogeneous, while arrays (like array or NumPy) are fixed-type and homogeneous for efficiency.
Example answer:
Python lists are flexible, holding mixed data types and resizing dynamically. Arrays (like array module or NumPy) hold elements of a single data type, are more memory efficient, and faster for numerical ops.
5. What is the difference between global and local scope?
Why you might get asked this:
Assesses understanding of variable visibility and lifetime within a program.
How to answer:
Define each scope: global variables are script-wide, local are function-specific. Explain accessibility differences.
Example answer:
Global variables are defined outside functions, accessible anywhere. Local variables are defined inside a function, accessible only within that function's block. Scope determines where variables can be referenced.
6. What is an iterator in Python?
Why you might get asked this:
Evaluates understanding of the iteration protocol and how for loops work internally.
How to answer:
Describe an iterator as an object that provides the next() method. Explain its role in yielding elements one by one.
Example answer:
An iterator is an object representing a stream of data. It must implement the iter() method (returning itself) and next() method, which returns the next item or raises StopIteration.
7. Which collection does not allow duplicate members?
Why you might get asked this:
Tests knowledge of Python's built-in collection types and their unique properties.
How to answer:
Identify the specific collection type designed for unique elements.
Example answer:
The set collection in Python does not allow duplicate members. It automatically enforces uniqueness for all its elements.
8. What is inheritance in Python?
Why you might get asked this:
Assesses understanding of core object-oriented programming concepts.
How to answer:
Define inheritance as a mechanism for a class (child) to acquire properties (attributes and methods) from another class (parent). Mention code reusability.
Example answer:
Inheritance is an OOP principle where a new class (child/derived) derives properties (attributes and methods) from an existing class (parent/base). It promotes code reusability and establishes 'is-a' relationships.
9. How does Python manage memory? Explain reference counting and garbage collection.
Why you might get asked this:
Tests understanding of Python's internal memory management mechanisms.
How to answer:
Explain reference counting as the primary method. Describe how objects are deallocated when ref count is zero. Mention the cyclic garbage collector for circular references.
Example answer:
Python uses reference counting; objects are deallocated when no variables reference them. A cyclic garbage collector handles reference cycles where objects reference each other but aren't accessible externally.
10. Does Python support multiple inheritance?
Why you might get asked this:
Checks knowledge of Python's OOP features, specifically its ability to inherit from multiple classes.
How to answer:
Confirm that Python supports it and briefly mention MRO (Method Resolution Order).
Example answer:
Yes, Python supports multiple inheritance. A class can inherit from several parent classes, and the order in which methods are searched is determined by the Method Resolution Order (MRO).
11. Difference between list and tuple?
Why you might get asked this:
A fundamental question reinforcing the mutability concept.
How to answer:
Focus on the key difference: mutability vs. immutability. Mention practical implications like performance or usage for fixed data.
Example answer:
The main difference is mutability: lists are mutable (can be changed after creation), while tuples are immutable (cannot be changed). Tuples are often used for fixed collections and are slightly faster.
12. What is slicing in Python?
Why you might get asked this:
Tests knowledge of a common and powerful operation on sequences.
How to answer:
Define slicing as extracting a portion of a sequence using start, stop, and step indices. Provide the basic syntax.
Example answer:
Slicing is a technique to extract a sub-sequence (part of a string, list, tuple, etc.) using the syntax sequence[start:stop:step]. It returns a new sequence.
13. How is multithreading achieved in Python?
Why you might get asked this:
Evaluates understanding of concurrency and the GIL (Global Interpreter Lock).
How to answer:
Mention the threading module. Crucially, explain the GIL's impact on CPU-bound tasks but its effectiveness for I/O-bound tasks.
Example answer:
Multithreading is done using the threading module. Due to the Global Interpreter Lock (GIL), Python threads execute CPU-bound tasks sequentially but are effective for I/O-bound operations (like network requests) as threads can release the GIL.
14. Which is faster, Python list or NumPy arrays?
Why you might get asked this:
Checks awareness of performance differences between built-in lists and a common numerical library.
How to answer:
State clearly that NumPy arrays are faster for numerical operations. Briefly explain why (homogeneous, contiguous memory, optimized C code).
Example answer:
NumPy arrays are significantly faster than Python lists for numerical operations. This is because they store homogeneous data types contiguously in memory and use optimized C implementations for computations.
15. What is shallow copy vs deep copy in Python?
Why you might get asked this:
Tests understanding of how copying affects nested objects and memory.
How to answer:
Explain that shallow copy copies the outer object but references inner objects. Deep copy copies the outer object and recursively copies all inner objects.
Example answer:
A shallow copy creates a new object but inserts references to the original objects found in the source. A deep copy creates a new object and recursively copies all nested objects, creating a completely independent copy.
16. What is PEP 8?
Why you might get asked this:
Assesses awareness of Python's style guide and best practices.
How to answer:
Identify PEP 8 as the standard style guide for Python code. Mention its purpose (readability, consistency).
Example answer:
PEP 8 is the official Python Enhancement Proposal that provides style guidelines for writing Python code. It ensures consistency and readability across different Python projects and developers.
17. What does the break, continue, and pass statements do?
Why you might get asked this:
Evaluates understanding of control flow statements within loops and conditional blocks.
How to answer:
Define the function of each statement clearly and distinctly.
Example answer:
break exits the current loop entirely. continue skips the rest of the current loop iteration and proceeds to the next one. pass is a null operation placeholder, used where a statement is syntactically required but no action is needed.
18. How to delete a file using Python?
Why you might get asked this:
Tests practical knowledge of common file system operations using the standard library.
How to answer:
Provide the specific function and module needed to delete a file.
Example answer:
You can delete a file in Python using the os module, specifically the os.remove() function. You pass the path to the file as an argument: os.remove("filepath/filename.txt").
19. What are Python’s primary built-in data types?
Why you might get asked this:
Checks foundational knowledge of the basic building blocks of data in Python.
How to answer:
List the main categories and examples of data types.
Example answer:
Primary built-in data types include Text (str), Numeric (int, float, complex), Sequence (list, tuple, range), Mapping (dict), Set (set, frozenset), Boolean (bool), and Binary (bytes, bytearray).
20. What is the syntax to print the type of a variable?
Why you might get asked this:
Simple question to test knowledge of a basic introspection function.
How to answer:
Provide the function name and demonstrate its usage within a print statement.
Example answer:
You use the built-in type() function. The syntax to print the type of a variable is print(type(variable_name)).
21. How are classes created in Python?
Why you might get asked this:
Assesses fundamental understanding of object-oriented programming syntax.
How to answer:
Explain the syntax using the class keyword and mention the role of init.
Example answer:
Classes are created using the class keyword, followed by the class name and a colon. Inside the class block, you define attributes and methods, including the init constructor.
22. What is a Python expression?
Why you might get asked this:
Tests understanding of the distinction between expressions and statements.
How to answer:
Define an expression as code that evaluates to a value.
Example answer:
A Python expression is a combination of values, variables, operators, and function calls that the Python interpreter evaluates to produce a result or value. Examples: x + 5, len([1, 2]).
23. What is the difference between == and is in Python?
Why you might get asked this:
Evaluates understanding of value comparison vs. identity comparison.
How to answer:
Explain that == checks for value equality, while is checks if two variables refer to the same object in memory.
Example answer:
== compares the values of two objects to see if they are equal. is compares the identity of two objects to see if they refer to the exact same object in memory.
24. What is type conversion in Python?
Why you might get asked this:
Checks knowledge of changing data types, a common operation.
How to answer:
Define type conversion (casting) as changing a value's data type. Mention explicit (using functions) and implicit conversion.
Example answer:
Type conversion is the process of changing the data type of an object to another data type. This can be done explicitly using functions like int(), float(), str(), or implicitly by Python in some operations.
25. Name some commonly used built-in Python modules.
Why you might get asked this:
Tests familiarity with Python's standard library, demonstrating practical knowledge.
How to answer:
List a few common modules and briefly state their purpose.
Example answer:
Common built-in modules include os (operating system interaction), sys (system-specific parameters), math (mathematical functions), datetime (date/time handling), and random (generating pseudo-random numbers).
26. How can you make a Python script executable on Unix?
Why you might get asked this:
Tests practical knowledge of scripting and environment setup.
How to answer:
Explain the two necessary steps: adding the shebang line and setting execute permissions.
Example answer:
First, add a shebang line #!/usr/bin/env python3 at the top of the script. Second, give the script execute permission using the command chmod +x script_name.py in the terminal.
27. What is a lambda function?
Why you might get asked this:
Evaluates knowledge of anonymous, small functions.
How to answer:
Define a lambda function as a small, anonymous, inline function. Explain its syntax and typical use cases (e.g., with map, filter, sort).
Example answer:
A lambda function is a small anonymous function defined with the lambda keyword. It can take any number of arguments but can only have one expression. They are often used for short operations where a full def is unnecessary.
28. What is list comprehension?
Why you might get asked this:
Tests knowledge of a concise and "Pythonic" way to create lists.
How to answer:
Define list comprehension as a concise syntax for creating lists. Provide the basic structure and mention its efficiency.
Example answer:
List comprehension is a concise way to create lists in Python. The syntax is [expression for item in iterable if condition]. It's generally more readable and efficient than traditional loops for simple list creation.
29. Explain the process of compilation and linking in Python.
Why you might get asked this:
Assesses understanding of how Python code is processed before execution.
How to answer:
Explain that Python is compiled into bytecode (.pyc files), which is then executed by the Python Virtual Machine (PVM). Clarify that linking isn't a distinct step like in C/C++.
Example answer:
Python code is compiled into bytecode (.pyc files) before execution. This bytecode is interpreted by the Python Virtual Machine (PVM). Unlike languages like C, there isn't a separate linking phase; dynamic loading happens at runtime.
30. How to handle exceptions in Python?
Why you might get asked this:
Evaluates understanding of error handling best practices.
How to answer:
Describe the try-except block structure. Mention the optional else and finally clauses.
Example answer:
Exceptions are handled using try and except blocks. Code that might raise an error is put in try, and the error handling is in except. Optional else runs if no exception occurs, and finally always runs.
Other Tips to Prepare for a python interview questions
Preparing for python interview questions involves more than just memorizing answers; it requires a deep understanding of the language and the ability to apply concepts. "Practice is the key to success," as many seasoned developers will tell you. Start by reviewing foundational topics like data types, control flow, functions, and object-oriented programming. Work through coding challenges on platforms like LeetCode or HackerRank, focusing on using idiomatic Python. Understand common libraries relevant to the role you're seeking (e.g., Pandas and NumPy for data science, Flask or Django for web). Explaining your thought process aloud while solving problems is crucial; this is where tools like Verve AI Interview Copilot can be invaluable, providing real-time feedback on your explanations and technical depth. Remember that interviewers are looking for how you think, not just the correct answer. Don't be afraid to ask clarifying questions. For practicing articulation and getting expert feedback, consider utilizing Verve AI Interview Copilot, which offers AI-powered mock interviews tailored to technical roles. As Bjarne Stroustrup said, "Our most important tool is our mind." Sharpen it by practicing both coding and explaining your logic. Mock interviews with Verve AI Interview Copilot (https://vervecopilot.com) can significantly boost your confidence and refine your responses to common python interview questions. Supplementing your study with interactive practice, such as that offered by Verve AI Interview Copilot, makes preparation more effective.
Frequently Asked Questions
Q1: What's the difference between .py and .pyc files?
A1: .py files contain the Python source code, while .pyc files contain the compiled bytecode generated by the interpreter.
Q2: What is a docstring?
A2: A docstring is a string literal used to document modules, classes, functions, or methods, accessed via doc.
Q3: What is the GIL?
A3: The Global Interpreter Lock (GIL) is a mutex that protects access to Python objects, preventing multiple native threads from executing Python bytecode simultaneously.
Q4: How do you comment code in Python?
A4: Use # for single-line comments or triple quotes ('''Docstring''' or """Docstring""") for multi-line comments/docstrings.
Q5: What is pickling and unpickling?
A5: Pickling is serializing a Python object structure into a byte stream; unpickling is the reverse process of deserializing the byte stream back into an object.
Q6: What is polymorphism in Python?
A6: Polymorphism allows objects of different classes to be treated as objects of a common superclass, enabling methods to behave differently based on the object type.
