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

Python Basics easy

Replace negatives with zero

Implement a function that replaces all negative numbers in a list with zero.

lists loops conditionals

Strings & Text easy

Replace vowels with stars

Write a function that replaces every vowel in a given string with an asterisk.

strings transformation vowels

Strings & Text easy

Normalize quotes

Replace all typographic quote characters with straight ASCII quotes.

strings replacement unicode

Strings & Text easy

Replace Spaces with Dashes

Write a function that replaces every space in a string with a dash.

strings replace manipulation

Strings & Text easy

Replace multiple spaces

Implement a function that replaces every sequence of spaces with a single space.

strings whitespace normalization

Strings & Text easy

Replace template variables

Implement a function that replaces {{variable}} placeholders in a string using a dictionary, leaving unknown placeholders intact.

string-manipulation parsing template

Lists & Arrays easy

Linear Interpolation Array

Given an array with some None values, replace them by linear interpolation between the nearest known values.

arrays interpolation math

Dicts & Sets easy

Replace keys with a mapping

Write a function that renames keys in a dictionary according to a mapping, with duplicate handling.

dicts mapping transformation

Two Pointers & Sliding Window medium

Character Replacement Window

Given a string and a number k, find the length of the longest substring that can be made uniform by replacing at most k characters.

sliding-window two-pointers strings

Two Pointers & Sliding Window medium

Longest Repeating Character Replacement

Given a string and an integer k, return the length of the longest substring that can be made of identical characters after at most k replacements.

sliding-window strings hash-map

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

Showing 1–11 of 11 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.