[python] Check if an object exists

I need to check if Model.objects.filter(...) turned up anything, but do not need to insert anything. My code so far is:

user_pass = log_in(request.POST)  # form class
if user_pass.is_valid():
    cleaned_info = user_pass.cleaned_data
    user_object = User.objects.filter(email = cleaned_info['username'])

You can also use get_object_or_404(), it will raise a Http404 if the object wasn't found:

user_pass = log_in(request.POST) #form class
if user_pass.is_valid():
    cleaned_info = user_pass.cleaned_data
    user_object = get_object_or_404(User, email=cleaned_info['username'])
    # User object found, you are good to go!
    ...

I think the easiest from a logical and efficiency point of view is using the queryset's exists() function, documented here:

https://docs.djangoproject.com/en/stable/ref/models/querysets/#django.db.models.query.QuerySet.exists

So in your example above I would simply write:

if User.objects.filter(email = cleaned_info['username']).exists():
    # at least one object satisfying query exists
else:
    # no object satisfying query exists

If the user exists you can get the user in user_object else user_object will be None.

try:
    user_object = User.objects.get(email = cleaned_info['username'])
except User.DoesNotExist:
    user_object = None
if user_object:
    # user exist
    pass
else:
    # user does not exist
    pass

You can use:

try:
   # get your models
except ObjectDoesNotExist:
   # do something

the boolean value of an empty QuerySet is also False, so you could also just do...

...
if not user_object:
   do insert or whatever etc.