In article <[EMAIL PROTECTED]>,
Ron Garret <[EMAIL PROTECTED]> wrote:
Wow, this is really cool:
> What I'm really trying to do is to create enumerated types...
And the code I ended up with is:
# Inheriting from type, not object, is the key:
class enum_metaclass(type):
def __getitem__(self, index):
return self.vals[index]
def enum(vals):
class enum(object):
__metaclass__ = enum_metaclass
def __init__(self, val):
try:
self.val = type(self).vals.index(val)
except:
raise TypeError, "%s is not a valid %s" % (val, type(self))
enum.vals = vals
return enum
So now I can do, e.g.:
>>> e1 = enum(['a','b','c'])
>>> e1('a')
<__main__.enum object at 0x393c50>
>>> e1('x')
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 8, in __init__
TypeError: x is not a valid <class '__main__.enum'>
>>>
But I can also do this:
>>> for x in e1: print x
...
a
b
c
>>>
Note that there's no __iter__ method anywhere! It makes an interesting
little puzzle to figure out why this works. (It totally blew me away
when I first tried it. Took me about five minutes of head scratching to
figure it out.)
rg
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