How to define related consts in python?

Question

Is it pythonic to define related consts like this?

define:

class LinkChoices(object):
    FOLLOW, FRIENDSHIP, CLOSE_FRIENDSHIP, = 10, 20, 30,

using:

from  some_module import LinkChoices

link.status = LinkChoices.FOLLOW

Are there any cons of defining consts like this?

There is a lot of debate over what is pythonic and what isn't, this is fine so don't worry about it — jamylak, Mar 24 '13 at 11:29

score 1 · Answer 1 · edited May 23 '17 at 10:25

1

Yes, I think it's pretty Pythonic, except that I wouldn't use ALL_CAPS for the class name.

I also don't see the point in the trailing commas.

Finally, I personally would probably define one constant per line rather than lumping them together on the same line.

For further discussion, see How to create a constant in Python

edited May 23 '17 at 10:25

Community

1
1

answered Mar 24 '13 at 10:58

NPE

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Agreed, for OP: http://www.python.org/dev/peps/pep-0008/ – jamylak Mar 24 '13 at 10:59
1

@NPE I changed class names – kharandziuk Mar 24 '13 at 11:04

score 1 · Answer 2 · answered Mar 24 '13 at 11:33

As suggested in the linked thread, you can also be defensive and take measures against accidental redefinition of your constants, for example:

def const(cls):
    class _const(type):
        def __setattr__(self,name,value):
            raise ValueError("Can't rebind const(%s)" % name)
    class _(cls):
        __metaclass__ = _const
    return _

@const
class LinkChoices(object):
    FOLLOW, FRIENDSHIP, CLOSE_FRIENDSHIP, = 10, 20, 30,

LinkChoices.FOLLOW = 123 # raises ValueError

Don't know if this is "pythonic" though. I'd say rather not.

How to define related consts in python?

2 Answers2