Python Interviews – Top Questions & Answers for Web Developers
Python is a high-level, dynamically typed, interpreted programming language known for its readability and flexibility. It's widely used in web development, automation, data science, AI, and scripting.
Because it’s simple, has a huge ecosystem of libraries, excellent community support, strong readability, and is suitable for both beginners and complex enterprise applications.
- Simple & readable
- Interpreted
- Dynamically typed
- Object-oriented
- Extensive libraries
- Cross-platform
- Great for rapid development
PEP 8 is Python’s official style guide that defines how to format Python code for readability and consistency (naming, spacing, indentation, etc.).
Python 3 introduced cleaner syntax, Unicode support, improved libraries, and is the only supported version now. Python 2 is outdated and deprecated.
Namespaces store names mapped to objects. Examples:
- Local
- Global
- Built-in
A module is a Python file containing functions, variables, or classes. Example: math.py.
A package is a collection of modules inside a directory with an __init__.py file.
PIP is Python’s package manager used to install and manage external libraries.
A self-contained Python environment that isolates dependencies per project.
- int
- float
- string
- bool
- list
- tuple
- dict
- set
- List: Mutable
- Tuple: Immutable, faster, used for fixed data
An unordered collection of key-value pairs. Example: {"name": "John"}.
Sets are unordered collections with unique elements.
Converting one data type to another:
int("10")
float("5")
str(123)- Arithmetic
- Comparison
- Logical
- Assignment
- Bitwise
- Membership
- Identity
is→ compares identity==→ compares values
A small anonymous function written in one line.
square = lambda x: x * xA decorator modifies a function’s behavior without changing its code.
A generator returns values one at a time using yield. It saves memory and performance.
return→ ends functionyield→ pauses and resumes later
A short way to create lists:
[x*x for x in range(5)]{k: k*k for k in range(5)}Using try, except, finally, else.
It always executes, even when an exception occurs.
User-defined exceptions using classes inheriting from Exception.
Object-oriented programming treats everything as objects with attributes and methods.
- Class → blueprint
- Object → instance of a class
A class can use attributes/methods from another class.
A class inheriting from more than one parent class.
Different classes having methods with the same name but different behavior.
Wrapping data and methods inside a class with restricted access using private variables.
Hiding internal details and showing only essential features.
- Instance method → works with object
- Class method → works with class (
@classmethod) - Static method → general utilities (
@staticmethod)
Special methods like:
__init__, __str__, __len__, __add__.
Constructor method called when creating objects.
Refers to the current instance.
A mutex allowing only one thread at a time in CPython.
Using:
- Threading
- Multiprocessing
- AsyncIO
When tasks are CPU-heavy.
For I/O-heavy tasks.
AsyncIO keywords for writing asynchronous, non-blocking code.
Objects that return elements one at a time using __iter__ and __next__.
Manages resources like files using with keyword.
Automatic setup and cleanup of resources.
Opening, reading, writing, or closing files using open().
Read mode ("r").
read()→ entire filereadline()→ one linereadlines()→ list of lines
Using json module:
json.loads()
json.dumps()Applies a function to each item in an iterable.
Filters items based on a condition.
Reduces a sequence to a single value (from functools).
len(), sorted(), sum(), min(), max(), etc.
Extracting a part of a list:
nums[1:4]
Accessing from the end:
arr[-1]
Allows passing variable number of arguments as tuple.
Allows passing variable number of keyword arguments as dict.
Changing behavior of code at runtime.
A function that remembers values from its enclosing scope.
LEGB Rule:
- Local
- Enclosing
- Global
- Built-in
- Shallow copy → copies references
- Deep copy → copies full objects
Using copy module.
Extracting substring:
name[0:3]Using:
- f-strings
.format()%format
arr[::-1]Function calling itself.
It may cause a stack overflow.
- NumPy
- Pandas
- Django
- Flask
- Matplotlib
- TensorFlow
- FastAPI
A library for numerical computation using powerful arrays.
A library for data analysis with DataFrame support.
A high-level web framework following MVT pattern.
A lightweight web framework for APIs and small apps.
A modern, high-performance API framework based on async/await.
A Python ORM for database operations.
Using modules like:
sqlite3psycopg2mysql.connector
- Follow PEP 8
- Write clean functions
- Use virtual environments
- Use meaningful names
Testing individual components using unittest or pytest.
Simulating objects during testing.
Automated integration and deployment pipeline for code.
append()→ adds elementextend()→ adds list elements
An immutable set.
Gives index + value.
Combines two lists element-wise.
Same as lists.
Reverse traversal:
arr[::-1]
sort()→ modifies listsorted()→ returns new list
Measure of algorithm performance.
Searching sorted data using divide-and-conquer.
Applying multiple decorators to a function.
A class that creates classes.
"If it walks like a duck, it’s a duck." Type depends on behavior, not class.
Storing results for fast access using functools.lru_cache.
Pattern ensuring only one instance is created.
Converting objects to storable formats (JSON, Pickle).
- JSON → readable, cross-language
- Pickle → Python only, faster, unsafe
Running multiple threads concurrently.
Threads waiting indefinitely for resources.
Storing previous results for efficiency.
Examples:
- Reverse string
- Find duplicate numbers
- FizzBuzz
- Palindrome check
Because it enables fast development, clean code, massive libraries, strong community, and excellent support for AI, data science, APIs, and automation.