Recursively work out deltas of numbers in dictionaries

delta_dict.py

def delta_dict(a, b):
    result = {}
    for key in a.keys():
        if isinstance(a[key], dict):
            result[key] = delta_dict(a[key], b.get(key, {}))
        else:
            result[key] = a[key] - b.get(key, 0)
    return result
    
  if __name__ == '__main__':
    print(delta_dict({'a': {'c': 4, 'd': 2}, 'b': 2}, {'a': {'c': 8}, 'b': 4}))