class call in square brackets in django, python

Question

This snippet is from djangoproject.com tutorial. Can someone explain why this line is written in this way:

inlines =[ChoiceInline]

instead of

inlines = ChoiceInline

why there are square brackets around class ChoiceInline?

from django.contrib import admin
from naslovnica.models import Poll
from naslovnica.models import Choice

class ChoiceInline(admin.TabularInline):
    model = Choice
    extra = 3

class PollAdmin(admin.ModelAdmin):
    fieldsets = [
    (None,               {'fields': ['question']}),
    ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
    ]
    inlines =[ChoiceInline]
    list_display = ('question', 'pub_date', 'was_published_recently')
    search_fields = ['question']
    list_filter = ['pub_date']

admin.site.register(Poll, PollAdmin)

Thank you all for answers. I choosed Lafad just because im new to programming and his answer was easiest for me to undersood. But all of answers are meaningfull for me now. — user1406647
– user1406647, Commented Mar 10, 2014 at 15:10

Daniel Roseman · Accepted Answer · 2014-03-10 14:51:58Z

4

It's not a "class call". It's simply a list. You can have multiple inlines, hence the plural, and you need to have them inside a list or a tuple.

answered Mar 10, 2014 at 14:51

Daniel Roseman

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4 Comments

user1406647 Over a year ago

what is exactly inline? why it is written in class? do you know more about that? where i can read more about it?

Daniel Roseman Over a year ago

But that is explained in exactly the place where you got that code from.

Raydel Miranda Over a year ago

You could also have inlines =(ChoiceInline,). Where (ChoiceInline,) is a tuple of only one element.

user1406647 Over a year ago

@Daniel I am trying to figure out about what is inlines part of and i couldnt do that from that tutorial. so i asked for help here.

NPatel · Accepted Answer · 2014-03-10 14:53:24Z

1

inlines =[ChoiceInline] this is not a calling of class. This will create new list which has class as first element.

Class calling will be done as ChoiceInline().

answered Mar 10, 2014 at 14:53

NPatel

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2 Comments

user1406647 Over a year ago

can you describe more what inlines is and can there be more elements and also which kind? other elements are classes too?

NPatel Over a year ago

inline is list and ChoiceInline is class. When you declare inlines =[ChoiceInline] it will define inline as list with one element. inline[0] will return you ChiceInline class, not ChoiceInline object.

Louis · Accepted Answer · 2014-03-10 14:59:50Z

1

Inlines are a list of InlineModelAdmin, TabularInline or StackedInline. This allows you to add "inline" forms for related models.

https://docs.djangoproject.com/en/dev/ref/contrib/admin/#inlinemodeladmin-objects

The admin interface has the ability to edit models on the same page as a parent model. These are called inlines.

answered Mar 10, 2014 at 14:59

Louis

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Comments

Fernando Freitas Alves · Accepted Answer · 2014-03-10 15:04:21Z

It receives a list or a tuple of Classes, because Django uses it as a special ModelAdmin class, like an extension to BaseModelAdmin.

Internally, Django will instance this classes, as you can see here:

def get_inline_instances(self, request, obj=None):
    inline_instances = []
    for inline_class in self.inlines:
        inline = inline_class(self.model, self.admin_site)
        if request:
            if not (inline.has_add_permission(request) or
                    inline.has_change_permission(request, obj) or
                    inline.has_delete_permission(request, obj)):
                continue
            if not inline.has_add_permission(request):
                inline.max_num = 0
        inline_instances.append(inline)

    return inline_instances

For a better understand I suggest you to see the options file in django.contrib.admin : https://github.com/django/django/blob/master/django/contrib/admin/options.py

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