Python-如何实现有序的默认字典?

我想结合OrderedDict(),并defaultdict()collections一个对象,这应是一个有序的,默认情况下dict。

这可能吗?

回答:

以下内容(使用此食谱的修改版)对我有用:

from collections import OrderedDict, Callable

class DefaultOrderedDict(OrderedDict):

# Source: http://stackoverflow.com/a/6190500/562769

def __init__(self, default_factory=None, *a, **kw):

if (default_factory is not None and

not isinstance(default_factory, Callable)):

raise TypeError('first argument must be callable')

OrderedDict.__init__(self, *a, **kw)

self.default_factory = default_factory

def __getitem__(self, key):

try:

return OrderedDict.__getitem__(self, key)

except KeyError:

return self.__missing__(key)

def __missing__(self, key):

if self.default_factory is None:

raise KeyError(key)

self[key] = value = self.default_factory()

return value

def __reduce__(self):

if self.default_factory is None:

args = tuple()

else:

args = self.default_factory,

return type(self), args, None, None, self.items()

def copy(self):

return self.__copy__()

def __copy__(self):

return type(self)(self.default_factory, self)

def __deepcopy__(self, memo):

import copy

return type(self)(self.default_factory,

copy.deepcopy(self.items()))

def __repr__(self):

return 'OrderedDefaultDict(%s, %s)' % (self.default_factory,

OrderedDict.__repr__(self))

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