What does it do?
Cerberus validates plain Python dictionaries against a rulebook you define, checking that required keys exist, values are the right type, and numbers fall within acceptable ranges. It works like a checklist a nurse runs through before a procedure: is this field filled in, is that value within a safe range, is nothing missing. Because it works directly with Python’s native dictionaries rather than requiring special classes, it stays deliberately small and easy to drop into an existing project. You describe your validation rules as a dictionary too, keeping the whole system simple to read.
See it in action
This checks a dictionary containing someone’s name and age against a set of rules, reporting whether it passed and listing any problems it found.
from cerberus import Validator
schema = {"name": {"type": "string"}, "age": {"type": "integer"}}
v = Validator(schema)
print(v.validate({"name": "Ada", "age": 36}))
print(v.errors)Why would a non-developer care?
Plenty of everyday data, form submissions, configuration options, records pulled from a spreadsheet, naturally lives in Python as a dictionary, and Cerberus offers a straightforward way to make sure that data is trustworthy without adopting a heavier framework. It’s the kind of small, focused tool that quietly prevents bad data from causing bigger problems downstream.
Real-world examples
Cerberus was built as the validation engine for Eve, a Python REST API framework, and has since been used independently anywhere developers want dictionary validation without extra ceremony. It fills a niche between doing no validation at all and adopting a full schema library like Pydantic or marshmallow.
Who uses it
Developers who already work primarily with plain Python dictionaries and want simple validation rules without restructuring their code around classes.
How it compares to alternatives
It’s lighter-weight than Pydantic or marshmallow, both of which lean on class-based schemas, making Cerberus a better fit when your data is already just a dictionary and you want validation with minimal setup.
Fun fact
It’s named after Cerberus, the three-headed dog guarding the underworld in Greek mythology, a fitting mascot for something that stands guard over your data.