Basic Calculator
Implement a function that evaluates a simple arithmetic expression with +, -, *, / and parentheses.
Simplify Path
Implement a function that simplifies a Unix-style absolute file path to its canonical form.
Change directory manager
Implement a function that processes `cd` commands and returns the resulting absolute path.
Parse key-value lines
Parse structured key-value lines into a dictionary with support for quoted values and escaped characters.
Additive number sequence
Check whether a given digit string can be partitioned into a valid additive sequence where each term is the sum of the previous two.
Basic Calculator II
Evaluate a basic arithmetic expression with +, -, *, / following operator precedence.
Evaluate Reverse Polish Notation
Evaluate an arithmetic expression written in reverse Polish notation using a stack.
Decode String Stack
Decode a compressed string with repeated substrings like '3[a2[c]]' to 'accaccacc' using a stack-based approach.
Score of Parentheses
Given a balanced parentheses string, compute its score where () is 1 and concatenation sums, nesting multiplies by 2.
Decode Nested String
Implement a function that decodes a string with nested encoding patterns.
Extract JSON-like numbers
Parse a simplified JSON-like string without using the json module and sum all numbers found in it.
Base64 Encode/Decode
Implement two functions to encode and decode Base64 strings using the standard alphabet and padding.
Flatten nested JSON
Write a function that flattens nested JSON objects into a flat dictionary with dot-separated keys, handling lists and empty objects.
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.
Showing 1–14 of 14 challenges · medium
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.