Please explain where does 'obj' come from in the 'get_image' method?

Question

Django

class Movie(models.Model):
title = models.CharField('Title', max_length=100)
tagline = models.CharField('Slogan', max_length=100, default='')
descriptions = models.TextField('Description' )
poster = models.ImageField('Poster', upload_to='movies/')
year = models.PositiveSmallIntegerField('Release date', default=2019)
country = models.CharField('Country', max_length=30)
directors = models .ManyToManyField(Actor, verbose_name='Director', related_name='film_director')
actors = models.ManyToManyField(Actor, verbose_name='Actors', related_name='film_actor')
genres = models.ManyToManyField(Genre, verbose_name='Genres')
world_premiere = models.DateField('World Premiere', default=date.today)
budget = models.PositiveIntegerField('Budget', default=0, help_text='Indicate the price in dollars')
fees_in_usa = models.PositiveIntegerField('Fees in USA', default=0, help_text='Price in USD')
fees_in_world = models.PositiveIntegerField('Fees in the World', default=0, help_text='Price in USD')
category = models.ForeignKey(Category, verbose_name ='Category', on_delete=models.SET_NULL, null=True)
url = models.SlugField(max_length=130, unique=True)
draft = models.BooleanField('Draft', default=False)

def __str__(self):
return self.title

def get_absolute_url(self):
return reverse('movie_detail', kwargs={'slug': self.url})

def get_review(self):
return self.reviews_set.filter(parent__isnull=True)

class Meta:
verbose_name = 'Movie'
verbose_name_plural = 'Movies'

@ admin.register(Movie)
class MovieAdmin(admin.ModelAdmin):
"""Movie"""
list_display = ('title', 'category', 'url', 'draft')
list_filter = ('category', 'year' )
search_fields = ('title', 'category__name')
inlines = [MovieShotsInLine,ReviewInLine]
save_on_top = True save_as
= True
list_editable = ('draft',)
readonly_fields = ('get_image',)
fieldsets = (
(None, {
"fields": (("title", "tagline")),)
}),
(None, {
"fields": ("descriptions", ("poster", 'get_image'))
} ),
(None, {
"fields": (("year", "world_premiere", "country")),)
}),
("Actors", {
"classes": ("collapse",),
"fields": (("actors", "directors", "genres", "category")),)
}),
(None, {
"fields": (("budget","fees_in_usa", "fees_in_world")),)
}),
("Options", {
"fields": (("url", "draft")),)
}),
)

def get_image(self, obj):
if obj.poster:
return mark_safe(f' else:
return 'no photo'

get_image.short_description = 'Poster'

Answer 1

With the help of inheritance from ModelAdmin, django allows you to declaratively customize the admin interface. In this case, django finds the string "get_image" in readonly_fields and follows a predefined algorithm - it checks if the model has such a field. If not, is there a function defined with that name that takes only one argument. If not (our case), then it is checked whether the given subclass of ModelAdmin has a method with the same name and takes 2 arguments. If there is such a method, then it is called and the current object is passed as the second argument. So the answer to your question is that django calls this method and passes obj.
list_display documentation. Readonly_fields - work exactly the same

Answer 2

I mean from where? Have you heard of function arguments?