Django-Admin: CharField as TextArea

For this case, the best option is probably just to use a TextField instead of CharField in your model. You can also override the formfield_for_dbfield method of your ModelAdmin class:

class CabAdmin(admin.ModelAdmin):
    def formfield_for_dbfield(self, db_field, **kwargs):
        formfield = super(CabAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        if db_field.name == 'descr':
            formfield.widget = forms.Textarea(attrs=formfield.widget.attrs)
        return formfield

Ayaz has pretty much spot on, except for a slight change(?!):

class MessageAdminForm(forms.ModelForm):
    class Meta:
        model = Message
        widgets = {
            'text': forms.Textarea(attrs={'cols': 80, 'rows': 20}),
        }

class MessageAdmin(admin.ModelAdmin):
    form = MessageAdminForm
admin.site.register(Message, MessageAdmin)

So, you don't need to redefine a field in the ModelForm to change it's widget, just set the widgets dict in Meta.

You will have to create a forms.ModelForm that will describe how you want the descr field to be displayed, and then tell admin.ModelAdmin to use that form. For example:

from django import forms
class CabModelForm( forms.ModelForm ):
    descr = forms.CharField( widget=forms.Textarea )
    class Meta:
        model = Cab

class Cab_Admin( admin.ModelAdmin ):
    form = CabModelForm

The form attribute of admin.ModelAdmin is documented in the official Django documentation. Here is one place to look at.