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Python Coding
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925 challenges 556 easy 323 medium 46 hard

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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

Lists & Arrays easy

All Unique Values Keep Order

Remove duplicates from a list, keeping only the first occurrence of each value while preserving relative order.

deduplicate order list

Lists & Arrays easy

Is Subset of Another List

Write a function that returns True if every element in a given list exists in another list, ignoring duplicates.

subset membership lists

Lists & Arrays easy

Union of Two Lists

Implement a function that combines two lists and returns only unique elements.

Lists & Arrays easy

Intersection two lists length

Return the number of distinct elements that appear in both input lists.

lists sets intersection

Lists & Arrays easy

Running Total Window

Implement a function that returns a list of running totals, resetting to zero after each positive sum.

running-total sliding-window arrays

Showing 1–5 of 5 challenges · easy · Lists & Arrays

Lists & Arrays — Python coding challenges

What you will find here

This page lists lists & arrays challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.

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.