[Django]-Django: How can I create a multiple select form?

I did it in this way :

forms.py

class ChoiceForm(ModelForm):
    class Meta:
        model = YourModel

    def __init__(self, *args, **kwargs):
        super(ChoiceForm, self).__init__(*args, **kwargs)
        self.fields['countries'] =  ModelChoiceField(queryset=YourModel.objects.all()),
                                             empty_label="Choose a countries",)

urls.py

from django.conf.urls.defaults import * 
from django.views.generic import CreateView
from django.core.urlresolvers import reverse

urlpatterns = patterns('',
    url(r'^$',CreateView.as_view(model=YourModel, get_success_url=lambda: reverse('model_countries'),
        template_name='your_countries.html'), form_class=ChoiceForm, name='model_countries'),)

your_countries.html

<form action="" method="post">
    {% csrf_token %}
    {{ form.as_table }}
    <input type="submit" value="Submit" />
</form> 

It is works fine in my example, If you need something more, just ask me!!

Regarding to my second question this is the solution. An extending class:

from django import forms
from django.utils.encoding import force_unicode
from itertools import chain
from django.utils.html import escape, conditional_escape

class Select(forms.Select):
    """
    A subclass of Select that adds the possibility to define additional 
    properties on options.

    It works as Select, except that the ``choices`` parameter takes a list of
    3 elements tuples containing ``(value, label, attrs)``, where ``attrs``
    is a dict containing the additional attributes of the option.
    """
    def render_options(self, choices, selected_choices):
        def render_option(option_value, option_label, attrs):
            option_value = force_unicode(option_value)
            selected_html = (option_value in selected_choices) and u' selected="selected"' or ''
            attrs_html = []
            for k, v in attrs.items():
                attrs_html.append('%s="%s"' % (k, escape(v)))
            if attrs_html:
                attrs_html = " " + " ".join(attrs_html)
            else:
                attrs_html = ""
            return u'<option value="{0}"{1}{2}>{3}</option>'.format(
                escape(option_value), selected_html, attrs_html, 
                conditional_escape(force_unicode(option_label))
                )
            '''
            return u'<option value="%s"%s%s>%s</option>' % (
                escape(option_value), selected_html, attrs_html,
                conditional_escape(force_unicode(option_label)))
            '''
        # Normalize to strings.
        selected_choices = set([force_unicode(v) for v in selected_choices])
        output = []
        for option_value, option_label, option_attrs in chain(self.choices, choices):
            if isinstance(option_label, (list, tuple)):
                output.append(u'<optgroup label="%s">' % escape(force_unicode(option_value)))
                for option in option_label:
                    output.append(render_option(*option))
                output.append(u'</optgroup>')
            else:
                output.append(render_option(option_value, option_label,
                    option_attrs))
        return u'\n'.join(output)

class SelectMultiple(forms.SelectMultiple, Select):
    pass

Example:

OPTIONS = [
        ["AUT", "Australia", {'selected':'selected', 'data-index':'1'}],
        ["DEU", "Germany", {'selected':'selected'}],
        ["NLD", "Neitherlands", {'selected':'selected'}],
        ["USA", "United States", {}]
    ]

I know your problem has been solved but from my research on Django Multiple Checkbox I discovered that the best way or practice is to use django-multiselectfield package. You first need to install it using pip: pip install django-multiselectfield then add it to installed apps in settings.py; 'multiselectfield'. Import the package in your models.py file: from multiselectfield import MultiSelectField then below is how you go about your models and form:
Models code:

class Country(models.Model):
    COUNTRY_CHOICES = (
    ('Nigeria', 'Nigeria'),
    ('USA', 'USA'),
    ('UK', 'UK'),
    ('Ghana', 'Ghana'),
    )
    favourates = MultiSelectField(choices = COUNTRY_CHOICES)

form.py code:

class CountriesForm(models.Model):
    
    class Meta:
        model = Country

views.py code:
Import the form in the views then do the following in function view for the template to display the checkboxes.

def UserCountryLikes(request):
    if request.method == "POST":
        form = CountriesForm(request.POST)
        if form.is_valid():
            country.form = CountriesForm(commit=False)
            country.save()
    else:
        form = CountryForm()
    context = {
    'form':form,
    }
    return render(request, 'app_name_folder_template/form_template.html', context)

In the Template (form_template.html in the views.py) to display the form do the following:

  <form method="POST" enctype="multipart/form-data">
    {% csrf_token %}
    {{ form }}
    <input class="btn btn-info mt-3" type="submit" value="Add Drinks">

    </form>

Remember to run migrations and migrate

ModelMultipleChoiceField is your friend. A CharField is capable of storing one selection, but not multiple, without some extra work, which I would recommend against.

API doc for ModelMultipleChoiceField

You can also define countries field in your form class as

Countries = forms.MultipleChoiceField(widget=forms.SelectMultiple,
                                             choices=OPTIONS_TUPPLE)

I don’t know which one is better in SelectMultiple and CheckboxSelectMultiple but it also works.

For more details you can use django documentation about widgets.

Working with widget=forms CheckboxSelectMultiple is quite difficult when you want to select multiple values.
(Remember Multiple select is for ManytoMany key Field)

In this condition SelectMultiple is better as you can select multiple items with ctrl or select all items with ctrl+a.

class MyModalForm(forms.ModelForm):
    class Meta:
    model = MyModel
        widgets = {            
            'products': forms.SelectMultiple(attrs={'required': True})
        }

if you wants dynamic values for multiple select you can do this with init

class MyModalForm(forms.ModelForm):
    class Meta:
    model = MyModel
        widgets = {            
            'products': forms.SelectMultiple(attrs={'required': True})
        }
    def __init__(self, *args, **kwargs):
        selected_products = kwargs.pop('selected_products', None)   ##queryset returned from function
        self.fields['products'].queryset = selected_products
        self.fields['orders'].queryset = OrderModal.objects.filter(pk=2)