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A Django model field that uses a DSL to define, generate, and validate, custom forms

Project description

A Django model field that uses a DSL to define, generate, and validate, custom forms.

ParamField allows you to store something like this:

width: Decimal -> max:50.0 min:5.0
height: Decimal -> max:40.0 min:3.0
painted : Bool-> default:False
inscription: Text-> max_length:30

and generate the django equivalent form as needed:

from django import forms

class CustomForm(forms.Form):
    width = forms.DecimalField(max_value=50, min=5)
    height = forms.DecimalField(max_valur=40, min=3)
    painted = forms.BooleanField()
    inscription = forms.CharField(max_length=30)

This is useful for creating user defined forms, or custom per models forms.


It has been tested on

  • Python 3
  • Django 1.9, 1.10


From the repository

$ git clone
$ python install

or from pypi

$ pip intall django-param-field


Add param_field to INSTALLED_APPS


Add the field to your model:

from djang.db import models
from param_field import ParamField, ParamDict

class CustomProduct(models.Model):
    name = models.CharField(max_length=44)
    params = ParamField(blank=True, max_length=3000)

Now that you have a working model to create a new instance with its parameters write:

params = """
    width: Dimmension-> max:50.0 min:5.0
    height: Dimmension-> max:40.0 min:3.0"""

    name='Custom wooden box",

And the FormView that generates the forms from the model

from django.shortcuts import render, get_object_or_404
from django.views.generic import FormView
from django import forms
from .models import CustomProduct

class CustomProductFormView(FormView):
    template_name = 'product_form.html'
    form_class = forms.Form

    def dispatch(self, request, *args, **kwargs):
        """Find requested CustomProduct it's needed both in post and get
        requests so the form can be genereted"""
        pk = self.kwargs['pk']
        self.product = get_object_or_404(CustomProduct, pk=pk)
        return super().dispatch(request, *args, **kwargs)

    def get_context_data(self, **kwargs):
        """Send product info to template"""
        context = super().get_context_data(**kwargs)
        context['product'] = self.product
        return context

    def get_form(self, form_class=None):
        """Generate form form param_field"""
        # NOTE: params.form(...) will return None when it doesn't
        # containt any field.
        return self.product.params.form(**self.get_form_kwargs())

    def form_valid(self, form):
        """Do what ever you want with the form, at this point it's a
        validated django form like any other"""
        custom_parameters = form.cleaned_data

Read this blog post for a longer tutorial that includes an example on how to handle File and Image fields.


Each ParamField can have one or more fields with the following syntax

fieldname: type-> property: value
  • fieldname - A lowercase name starting with a letter and followed by letters, numbers, and/or underscores. The default max name length is 30 characters.
  • type - One of the supported field types (All starting with uppercase)
    • Bool
    • Decimal
    • Dimmension
    • Integer
    • Text
    • TextArea
    • File
    • Image
  • property - One or more of the properties supported by the field type followed by a value.
    • ALL: hidden. required, label, help_text
    • Bool: default
    • Integer: default, even, odd, max, min, choices
    • Decimal: default, max, min, choices, max_digits, max_decimals
    • Text: default, max_length, min_length, choices
    • TextArea: default, max_length
    • File: (doesn’t support hidden)
    • Image: (doesn’t support hidden)
  • value - One of the value types supported by the property to its left
    • Boolean - True/False
    • Decimal - 1.33, 6.44
    • Integer - 44
    • String - “string with scape "chars" “
    • Value list - [value, value, value]


The absolute limits for the fields properties are configurable through, for example PARAM_INT_MAX controls the max allowed value for integer max property, so creating a new Integer field where max is bigger will fail.

These are the available options with their default value:


# Max lengths for label and help_text strings

# Max and Min integer values, these have been chosen so integers don't cause
# problems when stored in any DB
PARAM_INT_MAX =  2147483647
PARAM_INT_MIN = -2147483648

# The maximum number of digits allowed and the max decimal places

# Decimal max and min (must have valid number of digits/decimals)
PARAM_DECIMAL_MAX = Decimal("9999999999999999.9999")
PARAM_DECIMAL_MIN = Decimal("-9999999999999999.9999")

# Dimmension digits/decimals

# Dimmension max and min
PARAM_DIMMENSION_MAX = Decimal("99999999.9999")

# Text/TextArea max length

# max_length used by ParamField when it isn't supplied


Once the app has been added to, you can run the tests with:

$ python test param_field



  • Better parser error messages

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