This textbook delves into the practical applications of surface and groundwater hydrology, as well as the environment. The Part I, "Practical Python for a Water and Environment Professional, " guides readers through setting up a scientific computing environment and conducting exploratory data analysis and visualization using reproducible workflows. The Part II, "Statistical Modeling in Hydrology, " covers regression models, time series analysis, and common hypothesis testing. The Part III, "Surface and Subsurface Water, " illustrates the use of Python in understanding key concepts related to seepage, groundwater, and surface water flows. Lastly, the Part IV, "Environmental Applications, " demonstrates the application of Python in the study of various contaminant transport phenomena.