This textbook is designed to serve as a text for a first course on data structures and algorithms, typically taught as the second course in the computer science curriculum. There are three key features: 1. A strong focus on problem solving introduces students to fundamental data structures and algorithms by providing a very readable text without introducing an overwhelming amount of new language syntax. 2. Algorithm analysis in terms of Big O running time is introduced early and applied throughout. 3. Python is used to facilitate the success of beginning students in using and mastering data structures and algorithms.