json_path

Extracts a single value from a dictionary or list using a JSON path expression. Returns the first match found, or a fallback value if the path is invalid or the result is null.

Syntax

json_path(path, obj)
json_path(path, obj, fallback_value)

Parameters

Name	Type	Required	Description
path	string	Yes	A JSON path expression specifying the location of the value to extract.
obj	dict or list	Yes	The dictionary or list to search.
fallback_value	any	Optional	The value to return if the path is invalid or resolves to null. Defaults to None.

Returns

Type: any

The value found at the specified path, or fallback_value if the path does not match or the value is null.

Examples

Extract a nested field:

json_path("name.first", [user_data])

If user_data is {"name": {"first": "Alice", "last": "Smith"}}, the result is "Alice".

Access a list element:

json_path("[0].name", [records])

If records is [{"name": "Alice"}, {"name": "Bob"}], the result is "Alice".

Use a fallback for missing data:

json_path("address.city", [user_data], "Unknown")

If user_data has no address field, the result is "Unknown".

Notes

• Supports advanced JSONPath expressions as provided by the jsonpath-ng library, including filtering ($[?age < 30].name) and arithmetic ($.foo + '_' + $.bar).
• Only the first matching value is returned. Use json_path_multi to retrieve all matches.
• If the path expression is malformed or causes an error, the fallback_value is returned.
• A result of 0 is treated as a valid value and will not trigger the fallback.