Shapely is a Python package for manipulation and analysis of planar features, using functions from the GEOS library (the engine of PostGIS) and a port of the JTS. Shapely is not concerned with data formats or coordinate systems but can be readily integrated with packages that are. Shapely only deals with analyzing geometries and offers no capabilities for reading and writing geospatial files. It was developed by Sean Gillies, who was also the person behind Fiona and Rasterio.

Shapely supports eight fundamental geometry types that are implemented as a class in the shapely.geometry module—points, multipoints, linestrings, multilinestrings, linearrings, multipolygons, polygons, and geometrycollections. Apart from representing these geometries, Shapely can be used to manipulate and analyze geometries through a number of methods and attributes.

Shapely has mainly the same classes and functions as OGR while dealing with geometries. The difference between Shapely and OGR is that Shapely has a more Pythonic and very intuitive interface, is better optimized, and has a well-developed documentation. With Shapely, you're writing pure Python, whereas with GEOS, you're writing C++ in Python. For data munging, a term used for data management and analysis, you're better off writing in pure Python rather than C++, which explains why these libraries were created.

For more information on Shapely, consult the documentation at https://toblerity.org/shapely/manual.html. This page also has detailed information on installing Shapely for different platforms and how to build Shapely from the source for compatibility with other modules that depend on GEOS. This refers to the fact that installing Shapely will require you to upgrade NumPy and GEOS if these are already installed.