Convert Binary Number List
Given a list of bits (0s and 1s) in most-significant-first order, return the equivalent integer value.
Insertion Sort
Implement insertion sort that sorts a list in-place and returns the same list.
Intersection two lists length
Return the number of distinct elements that appear in both input lists.
Running Total Window
Implement a function that returns a list of running totals, resetting to zero after each positive sum.
Normalize Array to Zero-One Range
Implement a function that normalizes a list of numbers to the range [0,1] using min-max scaling.
Boolean Mask Filter
Write a function that filters a list using a boolean mask and returns the matching elements as a list.
Flatten Multidimensional Lists
Write a function that flattens arbitrarily nested lists of integers into a single list.
Concatenate Horizontally
Write a function that horizontally concatenates two 2D lists into a new 2D list.
Rolling Window Mean
Given a list of numbers and a window size k, return a list of the means of every contiguous subarray of length k.
Linear Interpolation Array
Given an array with some None values, replace them by linear interpolation between the nearest known values.
One Hot Encode Labels
Given a list of categorical labels, return a list of one-hot encoded vectors based on the sort order of unique labels.
Average Salary by Department
Given a list of employee tuples (name, department, salary), return a dictionary mapping each department to its average salary.
Pad array edges
Implement a function that pads a list on both ends with a given value to a specified total length.
Word frequency
Return a dict mapping each word to its count in the sentence.
List intersection
Return the sorted list of elements common to both lists.
First non-repeating character
Find the index of the first character that appears only once.
Most frequent element
Return the element that appears most often in a list.
Merge dicts summing values
Write a function that merges two dictionaries by summing values for duplicated keys.
Are two lists the same multiset
Write a function that checks if two lists contain the same elements with the same multiplicities, ignoring order.
Word to Index Map
Create a function that returns a dictionary mapping each unique word to the index of its first occurrence.
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.
Nested get with dotted path
Implement a function that safely retrieves a value from a deeply nested dictionary using a dot-separated path, returning a default if any key is missing.
Showing 241–264 of 556 challenges · easy
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.