Django model field choices - wouldn't a dict be better?

Given a field;

domain_status_choices = (
    (1,'Live')
    (2,'Offline')
    (3,'Dev')
)
status = models.SmallIntegerField( choices=domain_status_choices )

I know I can get and set numeric representation and use get_status_display() to get the text label. But if a user posts status=Offline how can I get the numeric value in order to save it? I'd also 开发者_JAVA百科like to be able to validate that numbers or text values are in the list.

To me it makes more sense to use a dict. Here's my current method;

domain_status_choices = {
    1: 'Live',
    2: 'Offline',
    3: 'Dev',
}
status = models.SmallIntegerField( choices=domain_status_choices.iteritems() )
...
if input1 not in domain_status_choices.keys(): print "invalid"
if input2 not in domain_status_choices.items(): print "invalid"
status = [k for k, v in domain_status_choices.iteritems() if v == input3][0]

Is there a better way? Why is a tuple of tuples usually used?

I believe the keys of a dict are not guaranteed to be sorted (unless you use OrderedDict obviously). That is, you "might" get "Offline", "Dev", "Live" choices with your version.

Implementation note on dict.items:

Keys and values are listed in an arbitrary order which is non-random, varies across Python implementations, and depends on the dictionary’s history of insertions and deletions.

Expanding on my comment on @vicvicvic's answer:

t = [ 'Live', 'Offline', 'Dev', ]
status = models.SmallIntegerField( choices=[(i,t[i]) for i in range(len(t))] )
...
if not 0 <= int(input1) < len(t): print "invalid"
if input2 not in t: print "invalid"
status = t.index(input2)