example.py

from django import forms

from fields import DecimalInput

class ExampleForm(forms.Form):
    meu_campo = DeicmalInput()

fields.py

# -*- coding:utf-8 -*-

from django import forms

import widgets


class DecimalField(forms.DecimalField):
    widget = widgets.DecimalInput
    
    def clean(self, value):
        value = super(DecimalField, self).clean(value)
        value = value or 0
        try:
            return float(value)
        except ValueError:
            raise forms.ValidationError(u'Informe um valor válido, por exemplo 1.000,00 ou 2,45.')
        except TypeError:
            raise forms.ValidationError(u'Informe um valor válido, por exemplo 1.000,00 ou 2,45.')
    
    def widget_attrs(self, widget):
        return {'class': 'decimal'}

utils.py

from django.template.defaultfilters import floatformat


def add_class_to_attrs(attrs, new_class):
    classes = attrs.get('class')
    if classes:
        classes = ' '.join([classes, new_class])
    else:
        classes = new_class
    attrs['class'] = classes


def floatdot(value,precision=-1):
    value = floatformat(value,precision)
    value = force_unicode(value)
    value = value.replace('.',',')
    return intdot(value)

widgets.py

from django import forms

from utils import floatdot, add_class_to_attrs

class DecimalInput(forms.TextInput):

    def render(self, name, value, attrs=None):
        attrs = attrs if attrs else {}
        value = value or ''
        final_attrs = self.build_attrs(attrs, type=self.input_type, name=name)
        if isinstance(value, float):
            value = "%s" % floatdot(value, 2)
        add_class_to_attrs(final_attrs, 'decimal')
        final_attrs['alt'] = final_attrs.get('alt', 'decimal')
        return super(DecimalInput, self).render(name, value, final_attrs)
    
    def value_from_datadict(self, data, files, name):
        value = data.get(name, None)
        if value:
            value = value.replace('.', '').replace(',','.') # Remove Commas and points
        return value