您可以设置依赖于另一个词典条目的词典值吗? [英] Can you set a dictionary value dependant on another dictionary entry?
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问题描述
这是想法:
dict1 = {key1:3, key2:5, key3:key1+key2}
# so key3 relate to the value: 8 (3+5)
dict1.update({key2:6})
# key3 will now relate to the value: 9 (3+6)
我试图避免更新不必要的条目,并且在比较关系值时基于一系列查找和更新中已经计算出的值建立新的键值关系.字典的散列性对于使我在查找时或多或少地保持恒定的时间至关重要.
I'm trying to avoid updating more entries than necessary as well as building new relations of key-value that's based on values that has already been calculated in a series of lookups and updates while comparing values of relations. The dictionarys' hashability is crucial to get me a more or less constant time on lookup.
推荐答案
这不是一般的解决方案,但大致适用于您的示例:
This isn't a general solution but roughly works for your example:
class DynamicDict(dict):
def __getitem__(self, key):
value = super(DynamicDict, self).__getitem__(key)
return eval(value, self) if isinstance(value, str) else value
>>> d = DynamicDict(key1=3, key2=5, key3='key1+key2')
>>> d.update({'key2': 6})
>>> d['key3']
9
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