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copied!<p>You could use multiple inheritance aka <em>mixins</em>, to factor out the fields that are used in both Form and ModelForm. </p> <pre><code>class SwallowFormFields: airspeed_velocity = forms.IntegerField( ... ) is_migratory = forms.BooleanField( ... ) class AfricanSwallowForm(forms.ModelForm, SwallowFormFields): class Meta: model = AfricanBird class EuropeanSwallowForm(forms.Form, SwallowFormFields): pass </code></pre> <p><strong>UPDATE:</strong></p> <p>Since this does not work with Django metaprogramming, you either need to create a custom <code>__init__</code> constructor that adds the inherited fields to the object's fields list or you can add the references explicitly inside the class definition:</p> <pre><code>class SwallowFormFields: airspeed_velocity = forms.IntegerField() is_migratory = forms.BooleanField() class AfricanSwallowForm(forms.ModelForm): airspeed_velocity = SwallowFormFields.airspeed_velocity is_migratory = SwallowFormFields.is_migratory class Meta: model = AfricanSwallow class EuropeanSwallowForm(forms.Form): airspeed_velocity = SwallowFormFields.airspeed_velocity is_migratory = SwallowFormFields.is_migratory </code></pre> <p><strong>UPDATE</strong>:</p> <p>Of course you don't have to nest your shared fields into a class -- you could also simply define them as globals ...</p> <pre><code>airspeed_velocity = forms.IntegerField() is_migratory = forms.BooleanField() class AfricanSwallowForm(forms.ModelForm): airspeed_velocity = airspeed_velocity is_migratory = is_migratory class Meta: model = AfricanSwallow class EuropeanSwallowForm(forms.Form): airspeed_velocity = airspeed_velocity is_migratory = is_migratory </code></pre> <p><strong>UPDATE:</strong></p> <p>Okay, if you really want to DRY to the max, you have to go with the <strong>metaclasses</strong>.</p> <p>So here is how you may do it:</p> <pre><code>from django.forms.models import ModelForm, ModelFormMetaclass from django.forms.forms import get_declared_fields, DeclarativeFieldsMetaclass from django.utils.copycompat import deepcopy class MixinFormMetaclass(ModelFormMetaclass, DeclarativeFieldsMetaclass): def __new__(cls, name, bases, attrs): # default __init__ that calls all base classes def init_all(self, *args, **kwargs): for base in bases: super(base, self).__init__(*args, **kwargs) attrs.setdefault('__init__', init_all) # collect declared fields attrs['declared_fields'] = get_declared_fields(bases, attrs, False) # create the class new_cls = super(MixinFormMetaclass, cls).__new__(cls, name, bases, attrs) return new_cls class MixinForm(object): __metaclass__ = MixinFormMetaclass def __init__(self, *args, **kwargs): self.fields = deepcopy(self.declared_fields) </code></pre> <p>You can now derive your collections of formfields from MixinForm like this:</p> <pre><code>class SwallowFormFields(MixinForm): airspeed_velocity = forms.IntegerField() is_migratory = forms.BooleanField() class MoreFormFields(MixinForm): is_endangered = forms.BooleanField() </code></pre> <p>Then add them to the list of base classes like this:</p> <pre><code>class EuropeanSwallowForm(forms.Form, SwallowFormFields, MoreFormFields): pass class AfricanSwallowForm(forms.ModelForm, SwallowFormFields): class Meta: model = AfricanSwallow </code></pre> <p>So what does it do?</p> <ul> <li>The metaclass collects all the fields declared in your MixinForm</li> <li>It then adds custom <code>__init__</code> constructors, to make sure that the <code>__init__</code> method of the MixinForm gets magically called. (Otherwise you would have to call it explicitly.)</li> <li><code>MixinForm.__init__</code> copies the declared fields int the field attribute</li> </ul> <p>Please note that I am neither a Python guru nor a django developer, and that metaclasses are dangerous. So if you encounter weird behaviour better stick with the more verbose approach above :)</p> <p>Good Luck!</p>

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