Using Django DecimalField with Select Widget

I'm not sure if there is something special I should be doing but I have a model and form similar to the following;

# models.py
from django.db import models

class ObjectModel(models.Model):
    object = models.DecimalField(max_digits=10, decimal_places=2)

# my_settings.py
from decimal import Decimal 

object_choices = [
    (Decimal('1'),'1'),
    (Decimal('1.5'),'1.5'),
    (Decimal('2'),'2'),
    (Decimal('2.5'),'2.5'),
    (Decimal('3'),'2.5'),
]

# forms.py
from django import forms
from my_settings import object_choices
from models import ObjectModel

class ObjectForm(forms.ModelForm):
    object = forms.ChoiceField(choices = object_choices)
    class Meta:
        model = ObjectModel
        fields = ['object']

The form renders fine, and saves the object without any problem. I can see in the Django Admin that the value I select on the form gets saved to the model, and all the other fields (not shown above) render and work fine.

When I load a form to edit the model rather than create a new one, e.g

views.py
from forms import ObjectForm
...
form = ObjectForm(instance = obj)
...

The select widget which renders doesn't have an initial value. If I delete the definition for 'object' in the form definition and let it render with the default text input, everything works as expected and I can see the correct value, the same as I can see in the Django admin.

I have checked that I am defining the choices as Decimal objects, I've tried to change to a TypedChoiceField and I have tried to set the fields initial value in the form init but without any luck.

I've also tried to define the form field as a DecimalField with a Select widget, e.g:

#forms.py 
... 
object = forms.DecimalField(
    widget=forms.Select(
        choices = object_choices,
    )
)

I'm not sure if there is a fundamental incompatibility between DecimalField and ChoiceField or the Select widget, or if there is maybe something special I should be doing. I've searched other questions but there's nothing I can see which would suggest why what I am doing wouldnt work so any help would be appreciated.

Thanks.

I think I have found the problem and so am posting here for visibility should anyone else have the same issue as I looked for a long time before posting.

The problem here seems to be related to how the decimal field interprets and stores values to the format stipulated in the model, even which entered differently, but not being able to operate similarly backwards when the Select widget is looking for a match in the choices for an initial value.

For example, my model had the object defined as;

object = models.DecimalField(max_digits=10, decimal_places=2)

I think this means that it is stored with 2 decimal places, reguaradless of what is entered. E.g an entry of Decimal('3') would be stored as Decimal('3.00').

When compared as numbers these are considered equal, but when compared as strings they are not, for example;

>>> from decimal import Decimal
>>> a = Decimal('3')
>>> b = Decimal('3.0')
>>> a == b
True
>>> str(a) == str(b)
False

Because of this, my choices list were valid inputs for the field, but, from what I can tell, none of them matched the stored value, and so the initial value was unable to be mapped to one of the choices.

I have changed my choices as follows and now I can use the ChoiceField and Select widget OK.

# my_settings.py
from decimal import Decimal 

object_choices = [
    (Decimal('1.00'),'1'),
    (Decimal('1.50'),'1.5'),
    (Decimal('2.00'),'2'),
    (Decimal('2.50'),'2.5'),
    (Decimal('3.00'),'2.5'),
]

What I am not sure about is what would happen if now, after creating the model and populating the database with some values, I then wanted to change the model to store 3 decimal places. I dont know if objects previously saved would still have 2 decimal places and therefore my list would no longer work, or if they would all be "upgraded" to 3 decimal places.