Suppose i have : 

class Library(models.Model):
    name = models.CharField(max_length = 100)

class Books(models.Model):
    library = models.ForeignKey(Library)
    book = models.CharField(max_length = 100)

I want to create a new Books, we know we can fill the library on Books with just Library's id, but we can also use instance of Library. My question is, is it better if we just provide the id? If i want to use the instance, then i have to evaluate using .get(), then does it hit the database?

Additional question : From the docs, queryset are lazy, it does not hit the database till evaluated, so when does queryset evaluated?

python django
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