Question

(Using django as an example; the ForeignKey is implicit in the example)

>>> from coconuts.models import Coconut, Swallow
>>> c1 = Coconut.objects.get(id=1)
>>> s = Swallow.objects.get(id=1)
>>> c2 = s.coconuts_carried.filter(id=1)
>>> c1 == c2
True
>>> c1 is c2
False

My understanding is that ‘is’ tests identity, while == tests equality. In this case, c1 and c2 are the same exact object. Why “isn’t” they the same thing?

Answer 1

is compares python objects, not objects in your database. each query returns a new python objects, and so c and c2 are different.

to see this, try changing some of the properties of c or c2. Only one of them will change.

as can be seen from the docs,

c == c2

is equivalent to

c.id == c2.id