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
Active
Viewed 1.8k times
75
John McGehee
- 9,117
- 9
- 42
- 50
-
1It depends what you're trying to do. In many cases, neither approach is the Right Way. In this broad a question, it seems that both work fine. – Adam Smith Jan 23 '14 at 00:49
-
2I generally go with `__dict__` just to avoid another layer of parentheses. Flat is better than nested and all. – user2357112 Jan 23 '14 at 00:50
-
I guess `__dict__` being slightly faster is no surprise. Accessing object attributes is faster than calling a function. – aIKid Jan 23 '14 at 00:58
-
1I don't know why but using `vars` seems cooler, and a little more neat. I can imagine this is more useful for beginners. It would be easier to explain, "Getting the vars of an object". – aIKid Jan 23 '14 at 00:59
-
To me `__dict__` is more intuitive because I get back `dict` representation of an object. – Akavall Oct 06 '17 at 17:55
3 Answers
82
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')
Matthew Trevor
- 14,354
- 6
- 37
- 50
35
I'd use vars().
From: https://wiki.python.org/moin/DubiousPython#Premature_Optimization
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.
iljau
- 2,151
- 3
- 22
- 45
-
-
Since vars(obj) calls obj.__dict__(), you would be skipping this single call. But iljau recommends using vars() as it's more readable. – Leonardo Aoun Jan 24 '23 at 14:38
-
Using `.__dict__` to get a `dict` looks more readable to me than using `vars`. – David Rubio Apr 05 '23 at 11:30
22
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).
max
- 49,282
- 56
- 208
- 355