[Python-ideas] Dict-like object with property access
steve at pearwood.info
Tue Jan 31 01:28:53 CET 2012
Nick Coghlan wrote:
> *Outside* the standard library, it's "practicality beats purity" that
> wins. People *like* being able to type ".attr" instead of "['attr']"
> when a field name happens to be a legal identifier.
Yes, but people like all sorts of things that aren't good for them, and while
Python can and does allow people to shoot themselves in the foot, I don't
think we should be providing a standard foot-shooting class :)
As I see it, x.name is best used for attributes of the object, which typically
means that (1) in some sense, they are inherently part of the object; (2) they
come from a relatively small enumerated set of names which is usually fixed;
and (3) you are very unlikely to be added or deleting them from an object
(usually a static set rather than dynamic).
x['name'] is for the opposite cases:
(1) the key/value pairs are not inherently part of the object, but in some
sense are possessions of the object; (2) they come from a potentially
arbitrarily large set of names which could grow indefinitely large; and (3)
are usually dynamic rather than static.
In my experience, there are very few use-cases which fall between those two
dict. But I think the first place to put one would be a recipe on (say)
ActiveState's cookbook, and see what sort of feedback and use it gets.
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