Cannot have multiple model fields with same choices

Question

In my django model I am trying to set fields like this:

mouth = models.DecimalField(choices=SCALE, max_digits=2, decimal_places=1)
nose = models.DecimalField(choices=SCALE, max_digits=2, decimal_places=1)
persistance = models.DecimalField(choices=SCALE, max_digits=2, decimal_places=1)
rating = models.DecimalField(choices=SCALE, max_digits=2, decimal_places=1)

the choices are defined globally like this:

SCALE = ( (0.5*x, str(0.5*x)) for x in xrange(1,11) )

I register these fields in my admin.py file. The problem I have is that only the first field that is defined (in this case mouth), will display the choices list. The other ones wont display any list at all. The same scenario happens when I create a ModelForm instance and output it into a template: I dont get the list for the other fields.

Also if I try to inverse the order of the fields, It is still the first one that is displayed correctly, so it's not something related to the mouth field itself.

Is there an option I need to pass to make the fields more 'distinct'?

@Liarez: this is a generator expression.

bruno desthuilliers
– bruno desthuilliers

2013-10-14 12:33:49 +00:00
Commented Oct 14, 2013 at 12:33 — bruno desthuilliers
– bruno desthuilliers, Commented Oct 14, 2013 at 12:33

bruno desthuilliers · Accepted Answer · 2013-10-14 12:32:39Z

3

In your definition, SCALE is a generator expression, not a sequence, so the generator is very probably exhausted after the first iteration (on your first field using it). Try using a list comprehension instead, ie SCALE = [(0.5*x, str(0.5*x)) for x in xrange(1,11)]

answered Oct 14, 2013 at 12:32

bruno desthuilliers

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2 Comments

QuantumLicht Over a year ago

Yes indeed! I guess this is also why it is suggested to define choices inside the model class so it's less likely to exhaust the generator if you reuse it for other fields.

bruno desthuilliers Over a year ago

Making a generator a class attribute won't change anything - once a generator is exhausted, it's exhausted, period. The reasons why it's (usually) better to define choices in the model is mainly locality and cohesion.

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