How to add attributes to option tags in django ?

First of all, don't modify fields in __init__, if you want to override widgets use Meta inner class, if you want to override form fields, declare them like in a normal (non-model) form.

If the Select widget does not do what you want, then simply make your own. Original widget uses render_option method to get HTML representation for a single option — make a subclass, override it, and add whatever you want.

class MySelect(forms.Select):
    def render_option(self, selected_choices, option_value, option_label):
        # look at the original for something to start with
        return u'<option whatever>...</option>'

class LocModelForm(forms.ModelForm):
    icons = forms.ModelChoiceField(
        queryset = Photo.objects.filter(galleries__title_slug = "markers"),
        widget = MySelect(attrs = {'id': 'mydds'})
    )

    class Meta:
        # ...
        # note that if you override the entire field, you don't have to override
        # the widget here
    class Media:
        # ...

I had a similar problem, where I needed to add a custom attribute to each option dynamically. But in Django 2.0, the html rendering was moved into the Widget base class, so modifying render_option no longer works. Here is the solution that worked for me:

from django import forms

class CustomSelect(forms.Select):
    def __init__(self, *args, **kwargs):
        self.src = kwargs.pop('src', {})
        super().__init__(*args, **kwargs)

    def create_option(self, name, value, label, selected, index, subindex=None, attrs=None):
        options = super(CustomSelect, self).create_option(name, value, label, selected, index, subindex=None, attrs=None)
        for k, v in self.src.items():
            options['attrs'][k] = v[options['value']]
        return options

class CustomForm(forms.Form):
    def __init__(self, *args, **kwargs):
        src = kwargs.pop('src', {})
        choices = kwargs.pop('choices', ())
        super().__init__(*args, **kwargs)
        if choices:
            self.fields['custom_field'].widget = CustomSelect(attrs={'class': 'some-class'}, src=src, choices=choices)

    custom_field = forms.CharField(max_length=100)

Then in views, render a context with {'form': CustomForm(choices=choices, src=src)} where src is a dictionary like this: {'attr-name': {'option_value': 'attr_value'}}.

Here's a class I made that inherits from forms.Select (thanks to Cat Plus Plus for getting me started with this). On initialization, provide the option_title_field parameter indicating which field to use for the <option> title attribute.

from django import forms
from django.utils.html import escape

class SelectWithTitle(forms.Select):
    def __init__(self, attrs=None, choices=(), option_title_field=''):
        self.option_title_field = option_title_field
        super(SelectWithTitle, self).__init__(attrs, choices)

    def render_option(self, selected_choices, option_value, option_label, option_title=''):
        print option_title
        option_value = forms.util.force_unicode(option_value)
        if option_value in selected_choices:
            selected_html = u' selected="selected"'
            if not self.allow_multiple_selected:
                # Only allow for a single selection.
                selected_choices.remove(option_value)
        else:
            selected_html = ''
        return u'<option title="%s" value="%s"%s>%s</option>' % (
            escape(option_title), escape(option_value), selected_html,
            forms.util.conditional_escape(forms.util.force_unicode(option_label)))

    def render_options(self, choices, selected_choices):
            # Normalize to strings.
            selected_choices = set(forms.util.force_unicode(v) for v in selected_choices)
            choices = [(c[0], c[1], '') for c in choices]
            more_choices = [(c[0], c[1]) for c in self.choices]
            try:
                option_title_list = [val_list[0] for val_list in self.choices.queryset.values_list(self.option_title_field)]
                if len(more_choices) > len(option_title_list):
                    option_title_list = [''] + option_title_list # pad for empty label field
                more_choices = [(c[0], c[1], option_title_list[more_choices.index(c)]) for c in more_choices]
            except:
                more_choices = [(c[0], c[1], '') for c in more_choices] # couldn't get title values
            output = []
            for option_value, option_label, option_title in chain(more_choices, choices):
                if isinstance(option_label, (list, tuple)):
                    output.append(u'<optgroup label="%s">' % escape(forms.util.force_unicode(option_value)))
                    for option in option_label:
                        output.append(self.render_option(selected_choices, *option, **dict(option_title=option_title)))
                    output.append(u'</optgroup>')
                else: # option_label is just a string
                    output.append(self.render_option(selected_choices, option_value, option_label, option_title))
            return u'\n'.join(output)

class LocModelForm(forms.ModelForm):
    icons = forms.ModelChoiceField(
        queryset = Photo.objects.filter(galleries__title_slug = "markers"),
        widget = SelectWithTitle(option_title_field='FIELD_NAME_HERE')
    )