django foreign key save

Question

I have models for eg like this.

class Mp3(models.Model):
    title=models.CharField(max_length=30)
    artist=models.ForeignKey('Artist')

and Here is how the Artist models looks like:

class Artist(models.Model):
    name=models.CharField(max_length=100,default="Unknown")

I have created Artist with id 1. How I can create a mp3 that is assigned to this artist?(I want need it for query like this for eg.

mp3=Mp3.objects.get(id=50)
mp3.artist

)I have tried sth like this

newMp3=Mp3(title="sth",artist=1)

but I got than

ValueError: Cannot assign "1": "Mp3.artist" must be a "Artist" instance.

I understand the error but still don't know how to solve this. Thanks for any help Best Regards

Answer 1

I think that getting the artist from the database just to add it to the Mp3 model its unnecessary, if you already have the artist id you should do something like this:

new_mp3 = Mp3(title='Cool song', artist_id=the_artist_id)
new_mp3.save()

Note that the _id in the artist parameter, Django stores foreign keys id in a field formed by field_name plus _id so you can pass the foreign key id directly to that field without having to go to the database again to get the artist object.

If you don't need the artist object for something else in your code you should use this approach.

Answer 2

artist = Artist.objects.get(id=1)  
newMp3 = Mp3(title="sth", artist=artist)