Flatten nested dictionaries, compressing keys

Question

Suppose you have a dictionary like:

{\'a\': 1,
 \'c\': {\'a\': 2,
       \'b\': {\'x\': 5,
             \'y\' : 10}},
 \'d\': [1, 2, 3]}

Ho

Answer 1

This is similar to both imran's and ralu's answer. It does not use a generator, but instead employs recursion with a closure:

def flatten_dict(d, separator='_'):
  final = {}
  def _flatten_dict(obj, parent_keys=[]):
    for k, v in obj.iteritems():
      if isinstance(v, dict):
        _flatten_dict(v, parent_keys + [k])
      else:
        key = separator.join(parent_keys + [k])
        final[key] = v
  _flatten_dict(d)
  return final

>>> print flatten_dict({'a': 1, 'c': {'a': 2, 'b': {'x': 5, 'y' : 10}}, 'd': [1, 2, 3]})
{'a': 1, 'c_a': 2, 'c_b_x': 5, 'd': [1, 2, 3], 'c_b_y': 10}