Are there any other ways to iterate through the attributes of a custom class, excluding the in-built ones?

Question

Is there another way to iterate through only the attributes of a custom class that are not in-built (e.g. __dict__, __module__, etc.)? For example, in this code:

class Terrain:
    WATER = -1
    GRASS = 0
    HILL = 1
    MOUNTAIN = 2

I can iterate through all of these attributes like this:

for key, value in Terrain.__dict__.items():
    print("{: <11}".format(key), " --> ", value)

which outputs:

MOUNTAIN     -->  2
__module__   -->  __main__
WATER        -->  -1
HILL         -->  1
__dict__     -->  <attribute '__dict__' of 'Terrain' objects>
GRASS        -->  0
__weakref__  -->  <attribute '__weakref__' of 'Terrain' objects>
__doc__      -->  None

If I just want the integer arguments (a rudimentary version of an enumerated type), I can use this:

for key, value in Terrain.__dict__.items():
    if type(value) is int: # type(value) == int
        print("{: <11}".format(key), " --> ", value)

this gives the expected result:

MOUNTAIN    -->  2
WATER       -->  -1
HILL        -->  1
GRASS       -->  0

Is it possible to iterate through only the non-in-built attributes of a custom class independent of type, e.g. if the attributes are not all integral. Presumably I could expand the conditional to include more types, but I want to know if there are other ways I'm missing.

You seem to be searching for [flufl.enum](http://packages.python.org/flufl.enum/) — JBernardo, Jul 07 '12 at 03:13
For simple scripts like this, I always try to use the in-built modules if at all possible, but that module looks intriguing. — Ricardo Altamirano, Jul 07 '12 at 03:14
just make your `Terrain` class a subclass of `flufl.enum.Enum` and it's done — JBernardo, Jul 07 '12 at 03:15
Are you defining any methods or just attributes? If not defining methods, use a [dictionary](https://docs.python.org/2/tutorial/datastructures.html#dictionaries) instead. — Nomen Nescio, Jan 20 '16 at 19:01

score 19 · Accepted Answer · answered Jul 07 '12 at 03:09

19

I would use:

for key, value in Terrain.__dict__.items():
    if not key.startswith("__"):
        print(...)

Or I would create an actual enumerated type that did what I wanted.

answered Jul 07 '12 at 03:09

Ned Batchelder

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Isn't `Terrain.__dict__.items()` equivalent to vars(Terrain).items()? – DSM Jul 07 '12 at 03:10
For an actual enumerated type, something like [this](http://code.activestate.com/recipes/67107/) would probably suffice, right? Or is their code that you would use and recommend? – Ricardo Altamirano Jul 07 '12 at 03:26
You should check `key.endswith` too – John La Rooy Jul 07 '12 at 04:57
Naturally, for instance variables you'd need to use `self` .. so `for key, value in self.__dict__.items():` – FloatingRock Sep 03 '14 at 18:32

score 3 · Answer 2 · answered Jul 07 '12 at 03:24

3

You could try something like this:

class GenericClass(object): pass
class_builtins = set(dir(GenericClass))

terrain_attributes = {attr: getattr(Terrain, attr) for attr in dir(Terrain) if attr not in class_builtins}

answered Jul 07 '12 at 03:24

Joel Cornett

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John La Rooy · Answer 3 · 2012-07-07T04:56:26.663

1

Builtin attributes should start and end with '__' so:

[(k,v) for k,v in Terrain.__dict__.items() if not (k.startswith('__')
    and k.endswith('__'))]

Some people like to create their own __attributes__ so this code wouldn't work properly for them. Hey there's a reason why this namespace is reserved

You'll also have to check for __slots__

edited Jul 07 '12 at 04:56

answered Jul 07 '12 at 04:50

John La Rooy

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Are there any other ways to iterate through the attributes of a custom class, excluding the in-built ones?

3 Answers3