JSON (Javascript Object Notation)

Json is a popular format used in RESTful services and configurations.

Creating JSON Objects

Arjuna’s Json class provides with various helper methods to easily create a Json object from various sources:

  • from_file: Load Json from a file.

  • from_str: Load Json from a string.

  • from_map: Load Json from a mapping type object.

  • from_iter: Load Json from an iterable.

  • from_object: Load Json from a Python built-in data type object.

The loaded object is returned as one of the following:
  • JsonDict

  • JsonList

  • If allow_any is set to True, then from_file, from_str and from_object calls return the same object as passed, if it is not a mapping or iterable.

Json Class Assertions

Json class provides the following assertions:

  • assert_list_type: Validate that the object is a JsonList or Python list

  • assert_dict_type: Validate that the object is a JsonDict or Python dict

Automatic Json Schema Extraction

Given a Json object, you can extract its schema automatically:


This schema can be used for schema validation for another Json object.

JsonDict Object

JsonDict encapsulates the Json dictionary and provides higher level methods for interaction.

It has the following properties:
  • raw_object: The underlying dictionary

  • size: Number of keys in the JsonDict

  • schema: The Json schema of this JsonDict (as a JsonSchema object)

Finding Json elements in a JsonDict Object

You can find Json elements in JsonDict by using a key name or by creating a more involved JsonPath query.

  • find: Find first match using a key or JsonPath

  • findall Find all matches using a JsonPath

Matching Schema of a JsonDict Object

You can use a custom Json schema dictionary or a JsonSchema object to validate schema of a JsonDict object.


It returns True/False depending on the match success.

Asserting JsonDict Object

JsonDict object provides various assertions to validate its contents:

  • assert_contents: Validate arbitary key-value pairs in its root.

  • assert_keys_present: Validate arbitrary keys

  • assert_match: Assert if it matches another Python dict or JsonDict.

  • assert_schema Assert if it matches provided schema dict or JsonSchema.

  • assert_match_schema Assert if it has the same schema as that of the provided dict or JsonDict.

JsonList Object

JsonList encapsulates the Json list and provides higher level methods for interaction.

It has the following properties:
  • raw_object: The underlying dictionary

  • size: Number of keys in the JsonList

== Operator with JsonDict and JsonList Objects

== operator is overridden for JsonDict and JsonList objects.

JsonDict supports comparison with a JsonDict or Python dict.

JsonList supports comparision with a JsonList or Python list.

json_dict_1 == json_dict_2
json_dict_1 == py_dict

json_list_1 == json_list_2
json_list_1 == py_list

Modifying JsonSchema Object

JsonSchema object is primarily targeted to be created using auto-extraction using Json.extract_schema.

You can currently make two modifications to the JsonSchema once created:

  • mark_optional: Mark arbitrary keys as optional in the root of the schema.

  • allow_null: Allow null value for the arbitrary keys.