Count word occurrences
Write a function that takes a sentence and returns a dictionary of word counts.
Parse environment variables
Write parse_env_vars that parses KEY=VALUE lines into a dict, converting booleans/numbers and ignoring comments.
Filter by Age
Filter a list of person dictionaries by age and return their names.
Rank Employees by Salary
Sort a list of employee dictionaries by salary descending, tie-break by name, and return ranked strings.
Parse key=value pairs
Implement a parser that converts a space-separated 'key=value' string into a Python dictionary, supporting quoted values.
Average Salary by Department
Given a list of employee tuples (name, department, salary), return a dictionary mapping each department to its average salary.
Merge dicts summing values
Write a function that merges two dictionaries by summing values for duplicated keys.
Group names by first letter
Given a list of names, return a dictionary mapping each first letter to all names starting with that letter in original order.
Missing keys default zero
Write a function to sum numeric values from dictionaries, treating missing keys as zero.
Keys Sorted by Value Descending
Given a dictionary mapping strings to integers, return a list of keys sorted by value descending, and when values tie, alphabetically ascending.
Common Keys of Two Dictionaries
Implement a function that finds keys shared by two dictionaries and returns them sorted.
Mode of a list via counting
Implement a function that returns the mode of a list, resolving ties by the element that appears first.
Sort by frequency
Sort a list by element frequency descending, with ties broken by order of first occurrence.
Hash map merge
Write a function that merges two dictionaries recursively, combining values and preserving structure.
Group by Department
Implement a function that groups a list of employee dictionaries by department, returning a dictionary keyed by department with lists of employee dictionaries.
Top N per group
Implement top_n_per_group that returns the top N scores for each group from a list of (group, score) pairs.
Flatten nested JSON
Write a function that flattens nested JSON objects into a flat dictionary with dot-separated keys, handling lists and empty objects.
Parse table rows
Implement a function that converts a simple text table into a list of dictionaries.
Inner Join Two Tables
Write a function that inner joins two lists of dictionaries on a common key and returns the combined rows.
Showing 1–19 of 19 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.