4
我想扩展the autovivification example在nosklo以前的答案给出允许字典访问元组。如何使用元组访问深度嵌套的字典?
nosklo的解决方案是这样的:
class AutoVivification(dict):
"""Implementation of perl's autovivification feature."""
def __getitem__(self, item):
try:
return dict.__getitem__(self, item)
except KeyError:
value = self[item] = type(self)()
return value
测试:
a = AutoVivification()
a[1][2][3] = 4
a[1][3][3] = 5
a[1][2]['test'] = 6
print a
输出:
{1: {2: {'test': 6, 3: 4}, 3: {3: 5}}}
我有一个情况,我想设置一个给定任意下标的元组的节点。如果我不知道元组的深度有多少层,那么我如何设计一种方法来设置合适的节点?
我在想,也许我可以使用类似下面的语法:
mytuple = (1,2,3)
a[mytuple] = 4
,但我有拿出一个工作实现麻烦。
更新
我有一个基于@ JCash的回答完全工作示例:
class NestedDict(dict):
"""
Nested dictionary of arbitrary depth with autovivification.
Allows data access via extended slice notation.
"""
def __getitem__(self, keys):
# Let's assume *keys* is a list or tuple.
if not isinstance(keys, basestring):
try:
node = self
for key in keys:
node = dict.__getitem__(node, key)
return node
except TypeError:
# *keys* is not a list or tuple.
pass
try:
return dict.__getitem__(self, keys)
except KeyError:
raise KeyError(keys)
def __setitem__(self, keys, value):
# Let's assume *keys* is a list or tuple.
if not isinstance(keys, basestring):
try:
node = self
for key in keys[:-1]:
try:
node = dict.__getitem__(node, key)
except KeyError:
node[key] = type(self)()
node = node[key]
return dict.__setitem__(node, keys[-1], value)
except TypeError:
# *keys* is not a list or tuple.
pass
dict.__setitem__(self, keys, value)
可实现输出一样使用扩展切片音符上面:
d = NestedDict()
d[1,2,3] = 4
d[1,3,3] = 5
d[1,2,'test'] = 6
'node = node [i] = type(self)()'似乎不能正常工作。我不得不把它分成两个单独的作业。你知道为什么吗? – 2013-02-26 03:23:33
嗯,不,我不知道我害怕。 – JCash 2013-03-02 15:00:21