The Python Materials Genomics (pymatgen) library is a robust, open-source Python library designed for materials analysis. It aims to facilitate high-throughput computational materials science by providing a comprehensive set of tools for initial setup, structure generation, thermodynamic analysis, and post-calculation data analysis. The library defines core Python objects for materials data representation, offers well-tested structure and thermodynamic analysis tools, and serves as an open platform for collaborative development. Pymatgen is integrated with the Materials Project's RESTful API, enabling users to access and analyze materials data efficiently. The library includes modules for compound generation, structure transformations, data assimilation, reaction calculation, phase diagram generation, and more. An example application demonstrates how pymatgen can be used to analyze the phase and electrochemical stability of a newly synthesized material, Li6Sn5, with minimal computational resources. The library's capabilities and integration with the Materials Project aim to accelerate materials design and innovation.The Python Materials Genomics (pymatgen) library is a robust, open-source Python library designed for materials analysis. It aims to facilitate high-throughput computational materials science by providing a comprehensive set of tools for initial setup, structure generation, thermodynamic analysis, and post-calculation data analysis. The library defines core Python objects for materials data representation, offers well-tested structure and thermodynamic analysis tools, and serves as an open platform for collaborative development. Pymatgen is integrated with the Materials Project's RESTful API, enabling users to access and analyze materials data efficiently. The library includes modules for compound generation, structure transformations, data assimilation, reaction calculation, phase diagram generation, and more. An example application demonstrates how pymatgen can be used to analyze the phase and electrochemical stability of a newly synthesized material, Li6Sn5, with minimal computational resources. The library's capabilities and integration with the Materials Project aim to accelerate materials design and innovation.