Python中有辦法實現可下標訪問(subscriptable)的類嗎?

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This topic created in 5082 days ago, the information mentioned may be changed or developed.

想讓一個對象可下標訪問很簡單, 只要在它的類定義中實現__ getitem__就可以了.
可是我想讓一個類可以下標訪問, 應該怎麼做呢?
具體來說是要達到這個效果:

我知道getattr有同樣地作用, 但它既麻煩又不優雅.

標訪問

實現

5 replies • 1970-01-01 08:00:00 +08:00

arzon

Jul 13, 2012

貌似只有getattr了, 不知道麻烦从何而来
def __getattr__(self, name):
try:
return self[name]
except KeyError:
raise AttributeError(name)

013231

Jul 13, 2012

@arzon 你確定是在回答我的問題嗎?

hwywhywl

Jul 13, 2012

class TableMeta(type):
def __getitem__(cls, name):
return getattr(cls, name, None)

class Fruit(object):
Apple = 0
Pear = 1
Banana = 2

__metaclass__ = TableMeta

cute

Jul 13, 2012

继承UserDict

013231

Jul 14, 2012

感謝@hwywhywl的回答. 在Python中, 類同樣也是對象. 而一個類的類是由__metaclass__定義的, 默認是type. 所以想使一個類可下標訪問, 在它的__metaclass__中實現__getitem__即可. 關於__metaclass__的詳細解釋: http://stackoverflow.com/questions/100003/what-is-a-metaclass-in-python?answertab=votes#tab-top