Implementation of JsonPointer

json_pointer.py

def dereference(value, pointer):
    tokens = get_reference_tokens(pointer)

    current_value = value
    while tokens:
        current = tokens.pop(0)
        if current == "":
            return current_value
        elif isinstance(current_value, dict):
            if current in current_value:
                current_value = current_value[current]
            else:
                raise Exception('')
        elif isinstance(current_value, list):
            try:
                current_int = int(current)
            except Exception:
                raise Exception(f'Couldnt convert {current} to int')
            if 0 <= current_int < len(current_value):
                current_value = current_value[current_int]
            else:
                raise Exception('')
        else:
            raise Exception('')
    return current_value


def get_reference_tokens(pointer):
    tokens = pointer.split('/')
    tokens = tokens[1:] if tokens[0] == '' else tokens
    tokens = [token.replace('~1', '/') for token in tokens]
    return [token.replace('~0', '~') for token in tokens]

  
  
# tests
import unittest

from parameterized import parameterized

from jsonpointer import dereference, get_reference_tokens


class TestDereference(unittest.TestCase):

    @parameterized.expand([
        ('name', ('', ''), ''),
        ('name', ('value', ''), 'value'),
        ('name', (['value'], '/0'), 'value'),
        ('name', ({'key': 'value'}, '/key'), 'value'),
        ('get array from dict', ({'key': ['value']}, '/key'), ['value']),
        ('dict then array', ({'key': ['value']}, '/key/0'), 'value'),
    ])
    def test(self, name, inp, output):
        value, pointer = inp
        self.assertEqual(dereference(value, pointer), output)

    @parameterized.expand([
            ('name', (['value'], '/1'), Exception),
            ('name', ('value', '12'), Exception),
            ('name', (['value'], 'ab'), Exception),
    ])
    def test_exception(self, name, inp, exception):
        value, pointer = inp
        with self.assertRaises(exception):
            dereference(value, pointer)


class TestGetReferenceTokens(unittest.TestCase):

    @parameterized.expand([
        ('name', '/abc/cde', ['abc', 'cde']),
        ('name', '/abc/cde', ['abc', 'cde']),
        ('name', '/ab~1c/cde~0', ['ab/c', 'cde~']),
        ('name', '/~01', ['~1']),
        ('name', '/~10', ['/0']),
        ('name', '/key/value', ['key', 'value']),
    ])
    def test(self, name, inp, output):
        self.assertEqual(get_reference_tokens(inp), output)