[python][jsonpath-ng] Use JSONPath to update a specific location of a JSON document.

update-json-by-jsonpath.py

from jsonpath_ng import jsonpath, parse

def mod_func(orig, data, field):
    data[field] *= 2

data = {
    "foo": [
        {"baz": 1},
        {"baz": 2},
    ],
    "user": {
        "name": "what"
    }
}

expr = parse("user.name")
expr.update(data, "Wonder")
assert data == {'foo': [{'baz': 1}, {'baz': 2}], 'user': {'name': 'Wonder'}}

# Bad case below! we can only update if the specified path exists.
expr = parse("user.age")
expr.update(data, 18)  # No effect!

expr = parse("foo[*].baz")
expr.update(data, mod_func)
assert data == {'foo': [{'baz': 2}, {'baz': 4}], 'user': {'name': 'Wonder'}}