PySAL, the Python spatial analysis library, is an open source cross-platform library for geospatial data science with an emphasis on geospatial vector data written in Python. It supports the development of high level applications for spatial analysis, such as (1) detection of spatial clusters, hot-spots, and outliers, (2) construction of graphs from spatial data, (3) spatial regression and statistical modeling on geographically embedded networks, (4) spatial econometrics, and (5) exploratory spatio-temporal data analysis. The package has a rich history in formal spatial analysis and continues to expand in depth and scope.