python中字典是有序的嗎

>>> d = {'a':-1,'b':-1,'c':-1}>>> d
{'a': -1, 'c': -1, 'b': -1}>>> for k,v in d.items():
... print k,v
... 
a -1c -1b -1

>>> from collections import OrderedDict
>>> d = OrderedDict()
>>> d['a'] = 1
>>> d['b'] = 2
>>> d['c'] = 3
>>> d
OrderedDict([('a', 1), ('b', 2), ('c', 3)])
>>> for k,v in d.items():
... print k,v
... 
a 1
b 2
c 3

>>> d = {'a':-1,'b':-1,'c':-1}
>>> d
{'a': -1, 'b': -1, 'c': -1}
>>> for k,v in d.items():
... print(k,v)
... 
a -1
b -1
c -1