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More readable Enumeration class for Django choices

Author:
achimnol
Posted:
July 22, 2009
Language:
Python
Version:
1.0
Score:
4 (after 4 ratings)

We currently use two-level tuples to specify choices of a field in models or forms.

But, because it has only (value, verbose name) pair, the readability is bad whenever we indicate a specific choice value in our Python codes.

So I made a small class that does "magic" for this: A Named Enumeration.

Instead of myobj.status == 0, use myobj.status == STATUS.UNREVIEWED, for example.

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class Enumeration(object):
    """
    A small helper class for more readable enumerations,
    and compatible with Django's choice convention.
    You may just pass the instance of this class as the choices
    argument of model/form fields.

    Example:
        MY_ENUM = Enumeration([
            (100, 'MY_NAME', 'My verbose name'),
            (200, 'MY_AGE', 'My verbose age'),
        ])
        assert MY_ENUM.MY_AGE == 100
        assert MY_ENUM[1] == (200, 'My verbose age')
    """

    def __init__(self, enum_list):
        self.enum_list = [(item[0], item[2]) for item in enum_list]
        self.enum_dict = {}
        for item in enum_list:
            self.enum_dict[item[1]] = item[0]

    def __contains__(self, v):
        return (v in self.enum_list)

    def __len__(self):
        return len(self.enum_list)

    def __getitem__(self, v):
        if isinstance(v, basestring):
            return self.enum_dict[v]
        elif isinstance(v, int):
            return self.enum_list[v]

    def __getattr__(self, name):
        return self.enum_dict[name]

    def __iter__(self):
        return self.enum_list.__iter__()

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Comments

pbx (on July 23, 2009):

Nicely done.

(Someday, dict comprehension syntax will shave a couple lines off the init :)

#

daws (on December 20, 2011):

Why not 

def __init__(self, *enum_list):

and skip the square brackets on init?

#

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