A collection of code snippets that I use in my Django apps

Extends Django's ChoiceField to provide an empty label similar to a ModelChoiceField

• The empty_label parameter defaults to u"---------", but can be overridden
• A required field has the empty field choice prepended to the list, unless an initial value is provided.
• When the field is not required, the empty field choice is always included, regardless of whether an initial value exists

Based on https://gist.github.com/davidbgk/651080

Usage:

in forms.py:

class MyFormName(Form):

    suitability = EmptyChoiceField(required=False,choices=Suitability)

See this link for a full write-up with example: http://dashdrum.com/blog/2013/02/django-emptychoicefield/

This little mixin provides an easy way to declare a custom ErrorClass for a form

Usage:

in forms.py:

class MyFormName(CustomErrorClassFormMixin, ModelForm)

	error_class = MyCustomErrorListClass

Notes:

• The mixin must be declared before the form class in order to update the error_class in kwargs before the form's init() method fires
• The error_class attribute must be defined
• See NoAsteriskTextErrorList as an example of a custom ErrorList

A simple example of defining a custom ErrorList, this class changes the default rendering example to the as_text() method, and that method is slightly modified from the stock behavior to not include an asterisk before each error.

Usage:

in views.py

form = MyFormName(data=form_data, error_class=NoAsteriskTextErrorList)

Or try the CustomErrorClassFormMixin or CustomErrorClassViewMixin

ModelBase extends the Model class and provides a couple of features I like to see in all of my models.

• The fields created_on and updated_on keep track of when the object is created or modified
• The allow_delete property can be overridden for each model to indicate when a delete is safe. Helps avoid accidental cascading deletes.

Usage:

in models.py

class MyModel(ModelBase):
    # define fields - created_on and updated_on are already defined

    @property
    def allow_delete(self):
    	if # some condition #:
    		return False
    	return True

An example of a condition that could be used in the allow_delete function would be to check to see if there are any linked objects.

if len(MyModel.objects.get(id=self.id).anothermodel_set.all()) == 0:  ## Check for linked objects
    return False  ## objects are linked
return True ## OK to delete

Truncates the given string to the desired length at the nearest available space.

Usage:

short_name = truncate_to_space(full_name,10)

Uses the Django provided regular expression to validate an email address.

Usage:

if is_valid_email(email_field):
	send_email(email_field)

From http://tomforb.es/using-python-metaclasses-to-make-awesome-django-model-field-choices?pid=0

A metaclass that makes for simple ModelField choices

Usage:

in models.py (or wherever you wish):

class ActionType(Choice):
    AWAITING_APPROVAL = 'E'
    APPROVED = 'A'
    REJECTED = 'R'
    IN_PROCESS = 'I'
    TO_COMMITTEE = 'C'
    NEEDS_RESEARCH = 'N'

in forms.py:

class MyFormName(Form):

    action_type = ChoiceField(required=False,choices=ActionType)

When used with a class based view descendent from FormMixin, this will include the custom error_class value in the get_form_kwargs method.

Usage:

    views.py:

    class MyViewName(CustomErrorClassViewMixin, [a FormMixin descendant, such as CreateView])

        error_class = MyCustomErrorListClass

Note:

• The error_class attribute must be defined
• See NoAsteriskTextErrorList as an example of a custom ErrorList

Set of mixins to add a 2nd model with a one-to-one relationship to class based views

Additional instance varaibles hold the information for the 2nd model:

other_model - required other_form_class other_queryset other_object other_fields

Usage:

Use these three mixins with their corresponding class-based view. Define the additional instance variables as needed.

Example:

class MyUpdateView(OneToOneUpdateMixin, UpdateView):

    model=MyModel
    form_class = MyForm

    other_model=MyOtherModel
    other_form_class = MyOtherForm

Set of mixins to add formset processing to class based views

FormsetMixin is the parent class that provides most of the functionality. However, the get() and post() methods need to be subclassed to provide a value for self.object.

FormsetCreateMixin and FormsetUpdateMixin both handle the assignment of self.object as is appropriate for their function.

Usage:

Use FormsetCreateMixin and FormsetUpdateMixin along with the corresponding class-based view. Also, the instance variable detail_form_class should be defined.

Example:

class MyView(FormsetCreateMixin, CreateView):
    model = MyModel
    form_class = MyModelForm
    detail_form_class = MyFormest

Based on RelatedFieldWidgetWrapper, this version does the same thing outside of the admin interface.

See this link for a full write-up with example:

http://dashdrum.com/blog/2012/12/more-relatedfieldwidgetwrapper-the-popup/

Adds the ability to disable selected choices of a Select control

Usage:

in forms.py:

class MyForm(Form):
    def __init__(self, disabled, *args, **kwargs):
        super(MyForm, self).__init__(*args, **kwargs)
        if disabled:
            self.fields['my_field'].widget.disabled = disabled

    my_field = ModelChoiceField(widget=SelectDisabled(),queryset=MyModel.objects.all(),empty_label=None)

in views.py:

    ## Set a condition in the filter clause of the query to return
    ## the disabled items

    disabled = []
    for m in MyModel.objects.filter(##condition##).values_list('id'):
        disabled.append(m[0])

    form = MyForm( data=request.POST or None, disabled=disabled)

Based on code from a docs page of django-authtools, this app will mod the user forms in Admin to not ask for a password. This would be used when authentication is expected to come from outside, such as LDAP or SAML.

http://django-authtools.readthedocs.io/en/latest/how-to/invitation-email.html

Usage:

include 'snips.no_password', in the list of INSTALLED_APPS

Note that the createsuperuser management command is not affected by this app, and the administrator can still create a local superuser account with a password.