DRY fields

So, your app is growing nicely, but you find yourself repeating the same field definition in a bunch of models. The models themselves have nothing to do with each other, so an abstract base class isn't a fit, but at various points you want, say, prices to always be the same configuration of DecimalField, or titles to always allow the same size.

So, you could sub-class the fields to produce your own pre-configured fields, but sometimes you want to vary them a little... this price is nullable, that title has help_text, and so on.

Partially done

Enter the joy of functools.partial

Here's a little sample from a project I'm currently working on:

import functools

PriceField = functools.partial(
    models.DecimalField,
    decimal_places=2,
    max_digits=10,
)

So what have we got here? Now, on my models I can put:

class MyModel(models.Model):
    price = PriceField()
    tax = PriceField(
        null=True,
        blank=True,
        help_text='Where applicable.',
    )

So, now my two fields are DecimalFields, with the same digits, etc., but some differences.

How about an even more common case:

from django.utils import timezone

AutoDateTimeField = functools.partial(
    models.DateTimeField,
    default=timezone.now,
)