The shapefile is probably the most often-used data format for geographical vector data today. This file format was developed by Esri, based on a mostly open specification for data interoperability among Esri and other GIS software products. Although many other file formats have been introduced in an attempt to replace the shapefile, it remains a widely-used file format. These days, many third-party programming modules in Python exist for reading and writing shapefiles.

Although the name shapefile might suggest that there's only one file associated with it, a single shapefile requires in fact at least three files that need to be stored in the same directory in order to work correctly:

• A .shp file with the feature geometry itself
• A .shx file featuring a positional index of the feature geometry to allow seeking forwards and backwards quickly
• A .dbf file with columnar attributes for each shape

Shapefiles have their own structure. The main file (.shp) contains the geometry data, consisting of a single fixed-length header, followed by one or more variable-length records.