So the question arises: how to make UserProfile to appear inline in the User editing interface in admin?

The solution is to import UserAdmin class and add an InlineAdmin objet to the inlines list. But there is a simple trick: you need to unregister and then register an AdminModel class for a User model. Here is an example.

models.py

from django.db import models
from django.contrib.auth.models import User

class UserProfile(models.Model):
    website_url = models.URLField(verify_exists=False)
    user = models.ForeignKey(User, unique=True)

admin.py

from django.contrib import admin
from someapp.models import *
from django.contrib.auth.admin import UserAdmin

# Define an inline admin descriptor for UserProfile model
class UserProfileInline(admin.TabularInline):
    model = UserProfile
    fk_name = 'user'
    max_num = 1

# Define a new UserAdmin class
class MyUserAdmin(UserAdmin):
    inlines = [UserProfileInline, ]

# Re-register UserAdmin
admin.site.unregister(User)
admin.site.register(User, MyUserAdmin)

Thanks to James Lloyd for a MetaClasses.plist file content.

Rounding can be done with decimal.Decimal object’s quantize method. Use decimal.ROUND_HALF_UP flag to get a Symmetric Arithmetic Rounding.

For example:

>>> from decimal import Decimal, ROUND_HALF_UP
>>> Decimal("234.4535").quantize(Decimal("0.001"), ROUND_HALF_UP)
Decimal("234.454")
>>> Decimal("234.4534").quantize(Decimal("0.001"), ROUND_HALF_UP)
Decimal("234.453")
>>> Decimal("-234.4535").quantize(Decimal("0.001"), ROUND_HALF_UP)
Decimal("-234.454")
>>> Decimal("-234.4535").quantize(Decimal("0.001"), ROUND_HALF_UP)
Decimal("-234.454")

So, the “traditional” round function will look like this:

from decimal import Decimal, ROUND_HALF_UP

def round(d, digits=0):
    """
    Symmetric Arithmetic Rounding for decimal numbers

    d       - Decimal number to round
    digits  - number of digits after the point to leave

    For example:
    >>> round(Decimal("234.4536"), 3)
    Decimal("234.454")
    >>> round(Decimal("234.4535"), 3)
    Decimal("234.454")
    >>> round(Decimal("234.4534"), 3)
    Decimal("234.453")
    >>> round(Decimal("-234.4535"), 3)
    Decimal("-234.454")
    >>> round(Decimal("234.4535"), -1)
    Decimal("2.3E+2")
    """
    return d.quantize(Decimal("1") / (Decimal('10') ** digits), ROUND_HALF_UP) 

See updated description and usage instructions.