About

JSONBender is an embedded Python DSL for transforming dicts. It's name is inspired by Nickelodeon's cartoon series Avatar: The Last Airbender.

Installing

git clone [email protected]:Onyo/jsonbender.git
python setup.py install

Usage

JSONBender works by calling the bend() function with a mapping and the source dict as arguments. It raises a BendingException if anyting bad happens during the transformation fase.

The mapping itself is a dict whose values are benders, i.e. objects that represent the transformations to be done to the source dict. Ex:

import json

from jsonbender import bend, K, S


MAPPING = {
    'fullName': S('customer', 'first_name') + K(' ') + S('customer', 'last_name'),
    'city': S('address', 'city'),
}

source = {
    'customer': {
        'first_name': 'Inigo',
        'last_name': 'Montoya',
        'Age': 24,
    },
    'address': {
        'city': 'Sicily',
        'country': 'Florin',
    },
}

result = bend(MAPPING, source)
print(json.dumps(result))

{"city": "Sicily", "fullName": "Inigo Montoya"}

###Benders

####K

K() is a selector for constant values: It takes any value as a parameter and always returns that value regardless of the source dict.

####S

S() is a selector for accessing keys and indices: It takes a variable number of keys / indices and returns the corresponding value on the source dict:

MAPPING = {'val': S('a', 'deeply', 'nested', 0, 'value')}
ret = bend(MAPPING, {'a': {'deeply': {'nested': [{'value': 42}]}}})
assert ret == {'val': 42}

####F F() takes a function and optional args, and applies that function at bending time. It is useful for performing complex operations for which actual python code is necessary. F-benders can be composed with other benders using << and >> to make them receive arbitrary values at bending time. Ex:

MAPPING = {
    'total_number_of_keys': F(len),
    'number_of_str_keys': F(lambda source: len([k for k in source.iterkeys()
                                                if isinstance(k, str)])),
    'price_floor': S('price_as_str') >> F(float) >> F(int),
}
ret = bend(MAPPING, {'price_as_str': '42.2', 'k1': 'v', 1: 'a'})
assert ret == {'price_floor': 42,
               'total_number_of_keys': 3,
               'number_of_str_keys': 2}