Iterating Through a Database Django

Question

I have a model in my database called Item. This is the model

class Item(models.Model):
    item_title = models.CharField("Item title: ", max_length=50)
    item_description = models.CharField("Item description: ", max_length=200)
    starting_price = models.FloatField( default = 0)
    picture = models.ImageField(upload_to = 'gallery')
    finishTime = models.DateTimeField("Finish time: ")
    ownerID = models.ForeignKey(User, on_delete = models.CASCADE)
    higestBid = models.FloatField()
    highestBidderID = models.IntegerField(blank=True, default=-1)
    active = models.BooleanField(default = True)

I want to create a function in views.py , which will check the 'active' field of each item in the database. How can I do that? I have tried to do this:

items = list(Item.object.values())
for i in range(items):
  print(item[i].active)

However it does not work. Any help is appreciated

Why would you use values()? Why would you call list? Why would you use range? Why are you using an index? Why not just for item in Item.objects.all(): print(item.active)? — Daniel Roseman
– Daniel Roseman, Commented Nov 20, 2019 at 15:35

willeM_ Van Onsem · Accepted Answer · 2019-11-20 15:37:52Z

1

You should iterate over the queryset itself:

for item in Item.objects.all():
  print(item.active)

Please do not use .values() [Django-doc]. You should only use that for some specific cases, like grouping on a certain value. By working with objects, you will still use model objects, and thus certain logic you added on that object, is still accessible.

Furthermore it is often better not to use list(..). A QuerySet is lazy, and thus if you somehow never iterate over it, then it will not make the query. Furthermore you can then do extra filtering on an existing QuerySet.

edited Nov 20, 2019 at 15:37

answered Nov 20, 2019 at 15:35

willeM_ Van Onsem

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2 Comments

Unknown123 Over a year ago

Don't use all() if you don't need, it overloads yours db.

willeM_ Van Onsem Over a year ago

@Unknown123: You can not iterate over .objects is a Manager, not a QuerySet. You need at least .filter(..), .all(..), etc. to construct a QuerySet. As the Zen of Python says: explicit over implicit.

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