The Pumpkin Book (南瓜书) is a supplementary learning resource that provides detailed derivations and explanations for the mathematical formulas in the Watermelon Book (西瓜书), Zhou Zhihua’s classic Machine Learning textbook. Written from an undergraduate mathematics perspective, it aims to help readers who struggle with the omitted derivation details in the original text. The book serves as a self-study guide and reference for students learning ML fundamentals.