Practice Arena

Python Coding
Challenges

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925 challenges 556 easy 323 medium 46 hard

All Easy Medium Hard

All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Error Handling & Exceptions easy

Safe Float Parser

Write a function that safely converts a string to a float, returning None for invalid inputs.

float exception parsing

Error Handling & Exceptions easy

Parse Error Recovery

Parse a whitespace-separated string into a list of valid integers, skipping invalid tokens.

parsing exceptions error-handling

Regular Expressions easy

Non-greedy quantifier

Implement a function that uses a non-greedy regex to extract the shortest substring between two delimiters.

regex lazy quantifier string parsing

Regular Expressions easy

Named group extraction

Parse a log line into structured fields using named groups and re.match.

regex named-groups parsing

Stacks & Queues easy

Balanced brackets in string

Check if a string of brackets is properly balanced using a stack-based approach.

stack string parsing

Stacks & Queues medium

Evaluate Reverse Polish Notation

Evaluate an arithmetic expression written in reverse Polish notation using a stack.

stacks arithmetic parsing

Stacks & Queues medium

Decode String Stack

Decode a compressed string with repeated substrings like '3[a2[c]]' to 'accaccacc' using a stack-based approach.

stacks string parsing

Stacks & Queues medium

Score of Parentheses

Given a balanced parentheses string, compute its score where () is 1 and concatenation sums, nesting multiplies by 2.

stack string parsing

Stacks & Queues medium

Decode Nested String

Implement a function that decodes a string with nested encoding patterns.

stack string parsing

Datetime & Time Calculations easy

Format date output

Parse ISO date strings and format them into a friendly US-style date output.

datetime string-formatting date-parsing

Datetime & Time Calculations easy

Datetime to Unix timestamp

Parse a datetime string and convert it to a Unix timestamp assuming UTC.

datetime parsing timestamp

Datetime & Time Calculations easy

Quarter from date

Compute the quarter (1-4) for a date string like '2023-07-15'.

datetime date parsing

Datetime & Time Calculations easy

Month Start Date

Parse a date string and return the first day of its month in the same format.

datetime date-parsing formatting

Data Formats & Parsing medium

Extract JSON-like numbers

Parse a simplified JSON-like string without using the json module and sum all numbers found in it.

json parsing numbers

Data Formats & Parsing medium

Base64 Encode/Decode

Implement two functions to encode and decode Base64 strings using the standard alphabet and padding.

base64 encoding string

Data Formats & Parsing easy

Protocol definition

Parse a simple wire protocol string into a structured dictionary.

parsing protocol strings

Data Formats & Parsing easy

Config Parser Reader

Parse a simple INI-style configuration text into a nested dictionary.

parsing strings config

Data Formats & Parsing easy

Parse YAML-like dict

Parse a simple YAML-like text with indentation into a nested dictionary.

parsing yaml dictionary

Data Formats & Parsing medium

Flatten nested JSON

Write a function that flattens nested JSON objects into a flat dictionary with dot-separated keys, handling lists and empty objects.

json recursion dictionaries

Data Formats & Parsing medium

Unflatten JSON dict

Given a flat dictionary with keys like 'a.b.c', reconstruct the nested dictionary where each dotted segment becomes a nested level.

json dict parsing

Data Formats & Parsing easy

Parse email header

Write a function that parses a raw email header string and returns sender, recipient, and subject.

parsing strings email

Data Formats & Parsing easy

Update Row by ID

Given a list of CSV rows and target ID, replace the first matching row's value.

csv parsing list

Data Formats & Parsing easy

Parse CSV Row

Implement a robust function that parses a single CSV line into a list of fields, handling double quotes and escaped quotes.

csv parsing strings

Data Formats & Parsing easy

Parse Apache log line

Write a function that parses a single Apache access log line into a dictionary with IP, timestamp, request, status, and size.

parsing strings regex

Showing 49–72 of 73 challenges

Guide: free Python coding challenges

Practice Python by solving problems

PythonSkillset challenges are hands-on coding exercises from beginner to advanced. Open a challenge, read the problem, write Python in the split-pane editor, and run tests with Pyodide — no install required.

How to use the arena

Pick a category — basics, algorithms, strings, and more
Open a challenge, read the statement, and edit the starter code
Run tests, fix failures, then try a related quiz or tutorial lesson

Challenges vs tutorials and quizzes

Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.