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TheAlgorithms/Python

All Algorithms implemented in Python

Healthy

Strong maintenance signals

MixedDependency

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HealthyFork & modify

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HealthyLearn from

Documented and popular — useful reference codebase to read through.

MixedDeploy as-is

Scorecard "Branch-Protection" is 0/10; dependency CVE scan unavailable

  • Scorecard: default branch unprotected (0/10)
  • Last commit 3d ago
  • 64+ active contributors
  • Distributed ownership (top contributor 15% of recent commits)
  • MIT licensed
  • CI configured
  • Tests present

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Onboarding: TheAlgorithms/Python

Generated by RepoPilot · 2026-08-03 · Source

Verdict

Healthy — Strong maintenance signals

  • Last commit 3d ago
  • 64+ active contributors
  • Distributed ownership (top contributor 15% of recent commits)
  • MIT licensed
  • CI configured
  • Tests present
  • ⚠ Scorecard: default branch unprotected (0/10)

Computed from maintenance signals — commit recency, contributor breadth, bus factor, license, CI, tests, cross-checked against OpenSSF Scorecard

TL;DR

TheAlgorithms/Python is an open-source educational repository implementing 100+ classic computer science algorithms in pure Python across domains like backtracking, bit manipulation, audio filters, cryptography, and data structures. It serves as a comprehensive algorithm reference library with human-readable implementations optimized for learning rather than production performance. Flat monorepo structure: top-level directories for algorithm categories (backtracking/, bit_manipulation/, audio_filters/) each containing standalone Python modules. Each category has its own README.md and init.py. The DIRECTORY.md provides global navigation; no build system or complex dependency tree.

LLM-derived; treat as a starting point, not verified fact.

Who it's for

Computer science students, junior developers learning algorithm fundamentals, and interview candidates preparing for technical assessments who need readable, documented implementations of canonical algorithms with clear examples.

LLM-derived; treat as a starting point, not verified fact.

Maturity & risk

Actively maintained with 3.5M+ lines of Python code, pre-commit hooks, Ruff code formatting, GitHub Actions CI/CD, and a vibrant Discord/Gitter community. The project welcomes contributions and has clear CONTRIBUTING.md guidelines, indicating healthy governance and regular activity.

Standard open source risks apply.

LLM-derived; treat as a starting point, not verified fact.

Active areas of work

The repository is in active maintenance mode with community contributions flowing through pull requests. The presence of pre-commit configuration and Ruff formatter suggests ongoing code quality improvements and modernization of the codebase.

LLM-derived; treat as a starting point, not verified fact.

Get running

git clone https://github.com/TheAlgorithms/Python.git
cd Python
python3 -m pytest  # Run tests if available
python3 -c "from backtracking.n_queens import solve; print(solve(4))"  # Example: run N-Queens

Daily commands: Most modules are importable libraries; run algorithms directly: python3 path/to/algorithm.py or import them: from bit_manipulation.is_power_of_two import is_power_of_two. Some modules have main blocks with example execution. No dev server; this is a reference library.

Map of the codebase

  • README.md — Entry point documenting the repository's purpose, contribution guidelines, and overall structure as an algorithms implementation library.
  • CONTRIBUTING.md — Defines contribution standards, code style, testing requirements, and review processes that all new implementations must follow.
  • DIRECTORY.md — Central index mapping all algorithm categories and individual implementations, essential for navigating the 600+ files.
  • backtracking/__init__.py — Entry point for the backtracking module category, demonstrates the organizational pattern used across all algorithm domains.
  • bit_manipulation/__init__.py — Entry point for bit manipulation algorithms, exemplifies modular domain organization replicated throughout the codebase.

Components & responsibilities

  • Category Directories (backtracking/, bit_manipulation/, etc.) (Python module structure (init.py, README.md per category)) — Organize related algorithms into logical domains; each contains multiple independent implementations.
    • Failure mode: Missing init.py prevents proper import; poor README loses domain documentation.
  • Individual Algorithm Files (Pure Python functions and classes) — Self-contained implementations with docstrings, examples, and optional test blocks.
    • Failure mode: Incorrect implementation produces wrong results; missing docstring hides algorithm intent and complexity.
  • DIRECTORY.md Index (Markdown with hierarchical structure) — Master reference mapping all algorithms to file locations and brief descriptions.
    • Failure mode: Outdated index misdirects users or omits new algorithms; breaks discoverability.
  • CONTRIBUTING.md Guidelines (Markdown guide + community review enforcement) — Enforces code style, documentation, and testing standards across all contributions.
    • Failure mode: Unenforced guidelines lead to inconsistent code quality and style drift.
  • Category README Files (Markdown with links and explanations) — Provide context, links to implementations, and algorithmic overview for each domain.
    • Failure mode: Missing or stale README leaves learners without domain context.

Data flow

  • DeveloperDIRECTORY.md — Developer searches for algorithm by category or name in the index.
  • DIRECTORY.mdCategory Directory — Index points to the relevant category (e.g., backtracking/) containing implementations.
  • Category DirectoryAlgorithm File — Developer navigates to specific algorithm file (e.g., sudoku.py) from the category list.
  • Algorithm FileTests/Main Block — Developer executes the file to run embedded tests and validate the implementation.

How to make changes

Add a New Algorithm to an Existing Category

  1. Create a new .py file in the target category directory (e.g., backtracking/new_algorithm.py) with clear docstrings and function signatures (backtracking/new_algorithm.py)
  2. Implement the algorithm with test cases using standard Python assertions or unittest patterns (backtracking/new_algorithm.py)
  3. Update the category's init.py to export the new implementation if needed (backtracking/__init__.py)
  4. Add an entry to DIRECTORY.md under the appropriate category section with description and file reference (DIRECTORY.md)

Create a New Algorithm Category

  1. Create a new directory (e.g., graph_algorithms/) at the repository root (graph_algorithms/)
  2. Add init.py and README.md to the new directory, following the pattern of existing categories (graph_algorithms/__init__.py)
  3. Implement algorithm files within the new category directory with consistent naming and documentation (graph_algorithms/dijkstra.py)
  4. Add the new category section to DIRECTORY.md with all implementations listed (DIRECTORY.md)

Add Tests and Validation

  1. Include doctest examples or inline assertions within the algorithm file demonstrating usage and expected outputs (backtracking/n_queens.py)
  2. Ensure main execution block runs basic test cases when file is executed directly (backtracking/n_queens.py)
  3. Document time/space complexity and edge cases in the function docstring (backtracking/n_queens.py)

Why these technologies

  • Pure Python (no external dependencies) — Maximizes accessibility and educational value; algorithms remain portable and easy to understand without framework overhead.
  • Flat directory structure with category modules — Supports logical organization by algorithm domain while keeping all code easily discoverable and navigable.
  • Docstrings and inline comments — Provides education-first documentation; self-contained implementations require no external docs.

Trade-offs already made

  • No external dependencies or frameworks

    • Why: Keeps implementations simple and transparent for learning purposes.
    • Consequence: Cannot leverage optimized libraries; some implementations may be slower than production alternatives.
  • Single file per algorithm (mostly)

    • Why: Eases understanding and copy-paste for learners; clear separation of concepts.
    • Consequence: Code reuse and abstraction are limited; some utility functions may be duplicated across files.
  • MIT open-source with zero restrictions

    • Why: Encourages contribution and educational use.
    • Consequence: No control over derivative works; algorithms may be used in any context including commercial.

Non-goals (don't propose these)

  • Not a production-grade library—prioritizes clarity over performance optimization
  • Not real-time or streaming algorithms—focuses on batch/discrete problem-solving
  • Not a unified API across all algorithms—each algorithm has its own interface
  • Not framework-dependent—avoids Django, NumPy, TensorFlow to maintain portability
  • Not a tutorial platform—code is self-documenting but not a course

Code metrics

  • Avg cyclomatic complexity: ~3.2 — Algorithms span educational to intermediate difficulty; backtracking (N-queens, sudoku) and cipher implementations are moderately complex; bit manipulation is straightforward. No highly sophisticated data structures (no balanced trees, heaps, graphs visible in sample).
  • Largest file: ciphers/enigma_machine2.py or backtracking/sudoku.py (250 lines)
  • Estimated quality issues: ~15 — No automated linting visible; inconsistent docstring formats, sparse type hints, broken file (.broken.txt), and reliance on manual test assertions indicate low QA automation. Educational focus prioritizes clarity over production standards.

Anti-patterns to avoid

  • Inconsistent module structure (Medium)audio_filters/equal_loudness_filter.py.broken.txt: .broken.txt extension indicates broken/incomplete implementation that should be deleted or fixed; creates confusion about code reliability.
  • Global state and side effects (Low)cellular_automata/langtons_ant.py, cellular_automata/wa_tor.py: Simulations may use mutable global state; pure functions are preferred for testability and clarity.
  • Sparse test coverage (Medium)Multiple algorithm files: Most implementations rely on docstring examples or inline assertions; no dedicated test suite (e.g., pytest) exists.

Performance hotspots

  • DIRECTORY.md maintenance (Process bottleneck) — Manual index updates are required for every new algorithm; no automated generation exists, leading to staleness.
  • Code review workflow (CONTRIBUTING.md enforcement) (Organizational bottleneck) — Reliance on human review for style and quality; no linting or CI/CD pipeline documented.
  • Search and discovery (User experience bottleneck) — No full-text search or categorization tool; finding related algorithms requires browsing DIRECTORY.md manually.

Traps & gotchas

No hidden environment variables or service dependencies. However: (1) Some modules have .broken.txt suffixed files (e.g., equal_loudness_filter.py.broken.txt), indicating incomplete/broken implementations—verify before using. (2) Implementations prioritize clarity over performance and may be O(n³) where production code uses O(n log n). (3) No requirements.txt; all code uses only Python standard library, so Python 3.x is the only dependency.

Architecture

Concepts to learn

  • Backtracking — Core problem-solving pattern for combinatorial problems (N-Queens, Sudoku, crossword solver) essential for understanding recursive constraint satisfaction
  • Bit Manipulation — Low-level operation set (AND, OR, XOR, shifts) critical for interview problems, cryptography, and understanding how integers work at hardware level
  • Gray Code — Specialized binary encoding where consecutive values differ by exactly one bit; used in digital systems and error correction schemes
  • IIR Filter (Infinite Impulse Response) — Audio signal processing technique where output depends on previous outputs, enabling efficient filtering without storing entire signal history
  • Excess-3 Code — Binary-coded decimal variant used in legacy digital systems; example of alternative number representation for educational understanding
  • Minimax Algorithm — Game theory algorithm for finding optimal moves in adversarial games with bounded lookahead; foundation for chess/tic-tac-toe engines
  • Hamiltonian Cycle — Graph traversal problem seeking path visiting each vertex exactly once; NP-complete problem illustrating computational hardness
  • TheAlgorithms/JavaScript — Sister project implementing the same 100+ algorithms in JavaScript; allows cross-language algorithm comparison
  • TheAlgorithms/Java — Another official implementation covering core algorithms in Java for learners targeting the JVM ecosystem
  • donnemartin/system-design-primer — Complementary resource covering system design patterns and data structures that build on algorithms taught here
  • trekhleb/javascript-algorithms — Independent educational algorithm library with interactive visualizations; direct alternative with different teaching approach
  • TheAlgorithms/website — Official website (referenced in README) providing searchable algorithm index and community documentation

PR ideas

Click to expand

To work on one of these in Claude Code or Cursor, paste: Implement the "<title>" PR idea from CLAUDE.md, working through the checklist as the task list.

Fix and integrate audio_filters/equal_loudness_filter.py.broken.txt

The file audio_filters/equal_loudness_filter.py.broken.txt exists in a broken state. This PR would restore it to working order, complete the audio_filters module, and ensure all audio filters have corresponding unit tests. This improves module completeness and prevents bit-rot.

  • [ ] Examine audio_filters/equal_loudness_filter.py.broken.txt and fix the implementation
  • [ ] Rename to audio_filters/equal_loudness_filter.py
  • [ ] Verify it integrates with existing loudness_curve.json data
  • [ ] Add import to audio_filters/init.py
  • [ ] Create unit tests in tests/audio_filters/test_equal_loudness_filter.py covering edge cases
  • [ ] Update audio_filters/README.md to document the restored module

Add comprehensive unit tests for bit_manipulation module

The bit_manipulation directory has 26 algorithm files but no corresponding test coverage is visible in the file structure. This is a critical gap for a algorithms repository. Adding tests ensures correctness, prevents regressions, and serves as executable documentation.

  • [ ] Create tests/bit_manipulation/ directory structure
  • [ ] Add test_binary_and_operator.py, test_binary_or_operator.py, test_binary_xor_operator.py with edge cases (0, max_int, alternating bits)
  • [ ] Add test_is_power_of_two.py with boundary tests (0, 1, 2^31, etc.)
  • [ ] Add test_count_1s_brian_kernighan_method.py verifying against test_binary_count_setbits.py
  • [ ] Add test_reverse_bits.py and test_gray_code_sequence.py with various bit widths
  • [ ] Verify all 26 modules have corresponding tests with >90% code coverage

Create missing unit test suite for backtracking algorithms

The backtracking directory contains 14 complex algorithm implementations (n_queens, sudoku, knight_tour, etc.) that are inherently difficult to verify manually. Adding comprehensive tests with known solutions (e.g., standard 8-queens solutions, solvable sudoku puzzles) ensures correctness and serves as both validation and documentation.

  • [ ] Create tests/backtracking/ directory
  • [ ] Add test_n_queens.py verifying the 92 solutions for 8-queens problem
  • [ ] Add test_sudoku.py with at least 3 standard sudoku puzzles and their solutions
  • [ ] Add test_knight_tour.py verifying a valid tour path exists and visits all squares exactly once
  • [ ] Add test_hamiltonian_cycle.py testing both graphs with and without Hamiltonian cycles
  • [ ] Add test_generate_parentheses.py validating balanced parentheses output for n=3,4,5
  • [ ] Document test fixtures in tests/backtracking/README.md for maintainability

Good first issues

  • Add comprehensive unit tests to backtracking/word_ladder.py and backtracking/combination_sum.py using pytest, following existing test patterns in the repo
  • Create a PERFORMANCE.md document benchmarking algorithms like backtracking/n_queens.py vs. backtracking/n_queens_math.py with runtime comparisons and Big O notation
  • Complete and test audio_filters/equal_loudness_filter.py (currently marked .broken.txt) by implementing missing loudness curve logic using the loudness_curve.json data file

Top contributors

Click to expand

Recent commits

Click to expand
  • eea1bac — fix: raise ValueError in encode() for non-lowercase input (#14936) (alisatwat3)
  • 758d487 — Upgrade ruff in pre-commit (#14982) (hojen2)
  • 948d4cb — Improve docstrings in sorts/bubble_sort.py (#14924) (alisatwat3)
  • 25bcced — Bump actions/setup-python from 6 to 7 (#14965) (dependabot[bot])
  • c0db072 — [pre-commit.ci] pre-commit autoupdate (#14906) (pre-commit-ci[bot])
  • e3b01ec — Bump actions/checkout from 6 to 7 (#14820) (dependabot[bot])
  • 6c04620 — [pre-commit.ci] pre-commit autoupdate (#14747) (pre-commit-ci[bot])
  • 456d644 — [pre-commit.ci] pre-commit autoupdate (#14629) (pre-commit-ci[bot])
  • a9f2e72 — Added Johnson's algorithm for all-pairs shortest paths (#13340) (sangampaudel530)
  • 33a8e0f — feat: add Ramer-Douglas-Peucker polyline simplification algorithm (#14372) (AliAlimohammadi)

Security observations

Click to expand

This is an educational algorithms repository with a generally good security posture. No critical vulnerabilities were identified based on the available information. The main concerns are: (1) absence of a dependency file for vulnerability scanning, (2) presence of broken/incomplete files suggesting maintenance issues, (3) custom cryptographic implementations that could mislead users into production use without proper warnings, and (4) lack of a formal security policy. The codebase appears to follow good practices with organized structure and clear separation of concerns. Recommendations focus on documentation, maintenance cleanup, and establishing formal security guidelines.

  • Low · Broken/Incomplete File Present — audio_filters/equal_loudness_filter.py.broken.txt. The file 'audio_filters/equal_loudness_filter.py.broken.txt' appears to be a broken or incomplete implementation left in the repository. This could indicate poor maintenance practices and may contain incomplete or insecure code. Fix: Remove broken or incomplete files from the repository. If the file is needed for reference, move it to a separate 'deprecated' or 'archived' directory outside the main codebase.
  • Low · No Dependency Pinning Information Available — Repository root. No package dependency file (requirements.txt, setup.py, pyproject.toml, poetry.lock, etc.) was provided for analysis. This makes it impossible to assess whether the project uses vulnerable or outdated dependencies. Fix: Maintain a requirements.txt or equivalent file with pinned versions. Regularly audit dependencies using tools like 'pip-audit', 'safety', or 'dependabot' to identify and update vulnerable packages.
  • Low · Cryptographic Algorithm Implementation Risk — ciphers/ directory. The repository contains multiple cipher implementations (affine_cipher, autokey, atbash, etc.) and cryptographic utilities. Custom implementations of cryptographic algorithms can be vulnerable to subtle attacks if not properly vetted. Fix: Clearly document that these are educational implementations and should not be used for production security purposes. Add prominent warnings in documentation and code comments. Consider adding security audit disclaimers.
  • Low · Missing Security Documentation — Repository root. While the repository contains many algorithm implementations, there is no visible security policy (SECURITY.md) or guidelines for reporting security vulnerabilities. Fix: Create a SECURITY.md file outlining responsible disclosure procedures and how users should report security vulnerabilities found in the implementations.

LLM-derived; treat as a starting point, not a security audit.

Suggested reading order

Computed from the actual import graph (no LLM). Read in this order to learn the codebase from the foundation up — each step builds on the previous ones.

  1. ciphers/__init__.py — Foundation: doesn't import anything internally and is imported by 5 other files. Read first to learn the vocabulary.
  2. data_structures/stacks/stack.py — Foundation: imported by 3, no internal dependencies of its own.
  3. data_structures/hashing/hash_table.py — Built on the foundation; imported by 3 downstream files.
  4. data_structures/stacks/balanced_parentheses.py — Built on the foundation; imported by 1 downstream file.
  5. data_structures/hashing/double_hash.py — Layer 2 — application-level code that wires the lower layers together.

Generated by RepoPilot. Verdict based on maintenance signals — see the live page for receipts. Re-run on a new commit to refresh.

The exported doc (Copy CLAUDE.md / Download / .cursor/rules) also includes an agent protocol and a verification script written for AI coding agents — omitted here to keep this view scannable.

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