May 26, 2018

System for describing and enforcing a Python object schema

Grouch is a system for describing and enforcing a Python object schema. That is, it provides you with a language for describing the intended type signatures of your objects collectively, the “object schema”, and tools to walk an object graph, checking that every value found matches your object schema.

An object schema describes every class in a collection of objects – in particular, it specifies the type of every instance attribute of every class. Grouch includes a type language for specifying attribute types, a tool to parse specially-formatted class docstrings and output a complete object schema, and another tool for walking a persistent object graph and ensuring that every scrap of data in it conforms to the object schema extracted from your class docstrings. The API for defining, querying, and enforcing types is fairly complete and well-documented, so you can use Grouch’s type system in other ways as well.

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