[英]Q&A: Defining __getitem__ method or assigning __getitem__ in classes
Which of the below is the recommended way to do __getitem__
, when it maps to an internal sequence type? 当
__getitem__
映射到内部序列类型时,建议使用以下哪种方法?
class A:
def __init__(self, ...):
...
self._internal_sequence = []
def __getitem__(self, key):
return self._internal_sequence[key]
class B:
def __init__(self, ...):
...
self._internal_sequence = []
def __getitem__(self, key):
# I'm pretty sure it won't be this one.
return self._internal_sequence.__getitem__(key)
class C:
_internal_sequence = []
__getitem__ = _internal_sequence.__getitem__
I realised my answer while writing the question, but I'll still post it here so others can benefit. 我在写问题时意识到了答案,但我仍将其张贴在这里,以便其他人受益。
C) This appears to work fine, until you realise the _internal_sequence is a class variable and will retain itself between classes. C)这似乎很好用,直到您意识到_internal_sequence是一个类变量并且将在各个类之间保留自己。 In addition, redefining
_internal_sequence = [...]
seems to remove the __getitem__
and cause IndexError
. 此外,重新定义
_internal_sequence = [...]
似乎删除了__getitem__
并导致IndexError
。
B) This doesn't look as nice as A) and for builtin types it will be slower - see here . B)看起来不如A)好,对于内置类型,它会更慢-请参见此处 。
Hence, A is the recommended way of mapping a class's __getitem__
to an internal sequence. 因此,A是将类的
__getitem__
映射到内部序列的推荐方法。
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