Question

I tried to run this example on my computer but when I restart the python surprisingly the created polls are saved to the database without a visible save statement.

Here is the code:

>>> from polls.models import Poll, Choice
>>> Poll.objects.all()[0].choice_set.create(choice='Not much', votes=0)
<Choice: Not much>

So I wonder by which statements save instructions are implied ? Because if I create it like this, it won’t survive a restart.

>>> c = Choice(choice='Not much3', votes=0)
>>> c.poll_id = 1

I am creating a choice and I am assigning the foreign key poll_id to the first poll. I know this shouldn’t last because I didn’t save. It is the first one that tricks me, I assume if I create it within the associated set it also automatically saves not only gives it’s proper foreign id.

I am also new to python, and semantics seemed just a little bit loose based on my prior experience on this issue. I’d expect first code to just assign the proper foreign id not also save it to the database.

Answer 1

Using the create() method on a QuerySet will automatically save the object, as specified in the documentation.

You can think of it as effectively an SQL INSERT statement.