Question

I have a model with field defined as

p = models.DecimalField(max_digits=12, decimal_places=6)

But the decimal_places=6 is only for internal accuracy. I only want 2 decimal_places to show up in the admin fields. So I thought perhaps I could do something with properties. But properties don t show up as fields in the Admin interface. E.g.: database record: 100.256754 admin edit field shows: 100.26

Is there a way to do this?

Answer 1

I m with wlashell -- your edit form should display the raw value; otherwise, you d be indirectly modifying the value each time the object got modified, even if the actual field wasn t changed at all. Probably not what you want.

If you d simply like to change the way the field displays in the change list (for readability, perhaps), you can define a method on your model class like so:

from django.db import models
from django.template.defaultfilters import floatformat

class MyModel(models.Model):
    p = models.DecimalField(max_digits=12, decimal_places=6, verbose_name= My Field Name )
    ...

    def display_p(self):
        """Format `p` to 2 decimal places, for readability."""
        return floatformat(self.p, 2)
    display_p.short_description =  My Field Name 
    display_p.admin_order_field =  p

Then, in your ModelAdmin subclass list_display you d include display_p instead of p:

from django.contrib import admin
from myapp.models import MyModel

class MyModelAdmin(admin.ModelAdmin):
    list_display = [ display_p , ...]
    ...

admin.site.register(MyModel, MyModelAdmin)

HTH.

Answer 2

If you want to simply display the value of the field but not make it editable you could use a custom template, or some javascript to mask / alter the value.

I have to question the wisdom though, of hiding the remaining digits from someone looking at the data. This smells like a disaster in the making as a person editing a field like that if you hid the values would not know what the full value is. If you really don t care about that from the user side, why store it in that manner at all.

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