Question

This doesn’t work:

>>> pa = Person.objects.all()
>>> pa[2].nickname
u'arst'
>>> pa[2].nickname = 'something else'
>>> pa[2].save()
>>> pa[2].nickname  
u'arst'

But it works if you take

   p = Person.objects.get(pk=2)

and change the nick.

Why so.

Answer 1

>>> type(Person.objects.all())
<class 'django.db.models.query.QuerySet'>

>>> pa = Person.objects.all() # Not evaluated yet - lazy
>>> type(pa)
<class 'django.db.models.query.QuerySet'>

DB queried to give you a Person object

>>> pa[2]

DB queried again to give you yet another Person object.

>>> pa[2].first_name = "Blah" 

Let’s call this instance PersonObject1 that resides in memory. So it’s equivalent to something like this:

>>> PersonObject1.first_name = "Blah"

Now let’s do this:

>>> pa[2].save() 

The pa[2] again queries a db an returns Another instance of person object, say PersonObject2 for example. Which will be unchanged! So it’s equvivalent to calling something like:

PersonObject2.save()

But this has nothing to do with PersonObject1.