Use `__dict__` or `vars()`?


Builtin function vars() looks more Pythonic to me, but I see __dict__ used more frequently.

The Python documentation indicates that they are equivalent.

One blogger claims that __dict__ is faster than vars().

Which shall I use?

Asked By: John McGehee



Generally, you should consider dunder/magic methods to be the implementation and invoking functions/methods as the API, so it would be preferable to use vars() over __dict__, in the same way that you would do len(a_list) and not a_list.__len__(), or a_dict["key"] rather than a_dict.__getitem__('key')

Answered By: Matthew Trevor

I’d use vars().


While a correctly applied optimization can indeed speed up code, optimizing code that is only seldom use [..] can make code harder to read. [..] Write correct code first, then make it fast (if necessary).

From: The Zen of Python

Readability counts.

Answered By: iljau

I agree vars should be preferred. My rationale is that, as python evolves, vars might be extended to do more than __dict__ does (for example, work for objects with slots, possibly in 3.7).

Answered By: max
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