In [3]: import yaml

In [4]: from collections import  OrderedDict

In [5]: d1 = OrderedDict()

In [6]: d1['a'] = 1

In [7]: d1['c'] = 2

In [8]: d1['b'] = 1

In [9]: d1
Out[9]: OrderedDict([('a', 1), ('c', 2), ('b', 1)])

In [10]: d = dict()

In [11]: d['a'] = 1

In [12]: d['c'] = 2

In [13]: d['b'] = 4

In [14]: d
Out[14]: {'a': 1, 'b': 4, 'c': 2}

In [16]: yaml.dump(d)
Out[16]: '{a: 1, b: 4, c: 2}\n'

In [17]: yaml.dump(d1)
Out[17]: '!!python/object/apply:collections.OrderedDict\ndictitems: {a: 1, b: 1, c: 2}\n'

In [18]: def setup_yaml():
   ....:       """ http://stackoverflow.com/a/8661021 """
   ....:       represent_dict_order = lambda self, data:  self.represent_mapping('tag:yaml.org,2002:map', data.items())
   ....:       yaml.add_representer(OrderedDict, represent_dict_order)
   ....:     

In [19]: setup_yaml()

In [20]: yaml.dump(d1)
Out[20]: '{a: 1, c: 2, b: 1}\n'