Update a nested dict with another one.

update_nested_dict.py

a = {
    'a': {
        'x': 1,
        'y': 2
    },
    'b': 3
}

b = {
    'a': {
        'x': 23
    },
    'b': 11,
    'c': 13
}

# We want to get {'a': {'y': 2, 'x': 23}, 'c': 13, 'b': 11}


def update_nested_dict(a, b):

    for k, v in b.items():
        if isinstance(v, dict):
            d = a.setdefault(k, {})
            update_nested_dict(d, v)
        else:
            a[k] = v
    return a

print update_nested_dict(a, b)