Converts a JSON Schema to a Plain Old Python Object class

python, json-schema, code-generator
pip install JSONSchema2PoPo2==2.2.0



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A converter to extract 'Plain Old Python Object' classes from JSON Schema files. Similar to the Java project JSONSchema2PoJo.

PyPI version Python package

Generated Code Compatibility

Language Feature Version Compatibility Reason
Python Basic generation Any Python N/A
Python Using Enums >= Python 3.4 Uses Enum type
Python Using Extends >= Python 3.0 Uses new style Python class for inheritance
Python Using Types >= Python 3.5 Uses Python type hints in code
JavaScript Basic Generation >= ES2019 (>= NodeJS 12.x) Uses ES classes and private fields
Go Basic Generation Any Go N/A


pip install jsonschema2popo2



jsonschema2popo2 -o /path/to/ /path/to/json_schema.json


  • -o, --output-file - Generated file path.
  • -t, --use-types - Add MyPy typings.
  • -ct, --constructor-type-check - Validate provided types in constructor. Default only type checks when setting property values and not when setting them in the constructor.
  • -s, --use-slots - Add a __slots__ to each generated class to be more memory efficient.
  • --no-generate-from-definitions - Don't generate any classes from the "definitions" section of the schema.
  • --no-generate-from-root-object - Don't generate any classes from the root of the schema.
  • -tp, --translate-properties - Translate property names to be snake_case. With this enabled, inner classes will no longer be prefixed by "_" since their names won't collide with the property name.
  • -l, --language - Language to generate in. Either "js" or "python".
  • --namespace-path - Namespace path to be prepended to the @memberOf for JSDoc (only used for JS)
  • --package-name - Package name for generated code (only used for Go). Default is "generated".

Encode Generated Object to JSON:


import json

g = GeneratedClass()


g = new GeneratedClass();


g := generated.GeneratedClass{};
str, err := json.Marshal(g)

Decode JSON into Generated Object:


import json
g = GeneratedClass.from_dict(json.loads(data))


const g = GeneratedClass.fromMap(JSON.parse(data));


var g generated.GeneratedClass
err := json.Unmarshal(data, &g)

JSON Schema Format

This library is largely compatible with JSONSchema2PoJo and how that library reads the JSON Schema to generate Java. Specifically, for enumerations, this library supports setting the javaEnumNames array in JSON Schema for an enum to give names to the enum values that will be generated in the Python output.

If you want to generate an object with a property that accepts any map/dictionary, then simply have "type": "object" in the schema and do not add any properties to that definition. In this case, no new class will be generated, instead that property's type will be dict in Python and Object in JavaScript.

Example JSON Schema Documents

Schema with references and enum

  "definitions": {
    "Enum1": {
      "description": "My favorite Enum!",
      "type": "integer",
      "enum": [1, 2, 3],
      "javaEnumNames": ["First", "Second", "Third"]
    "Obj1": {
      "type": "object",
      "properties": {
        "prop1": {
          "type": "string"
        "prop2": {
          "$ref": "#/definitions/Enum1"
    "Obj2": {
      "type": "object",
      "properties": {
        "obj1": {
          "$ref": "#/definitions/Obj1"

Generated Documentation

When you provide a "description" in the JSON Schema, then that description will be applied in docstrings in the generated code. For example, in the example above, the enum will have a docstring which says My favorite enum!.

You can also choose to add documentation for yourself in the schema document using the "$comment" key, which is simply ignored by this tool. In this way, you can have public documentation in the description, and anything you want to keep private can go in the $comment.