CODEWITHSUNDEEP
pythondjangomodel
SangminKim
SangminKim

Reputation: 9136

What is the best way to get an object which is not sure if there is or not in Django model

What is the best way to get an object which is not sure if there is or not.(in Django model)

I think there are three options.

One is to use try and except statement to process the exception.

Second is to use objects.filter() instead of objects.get() and check query_set.count().

Third is to use objects.count() first and then use objects.get() if there is.

Upvotes: 1

Views: 51

Answers (2)

Paulo Pessoa
Paulo Pessoa

Reputation: 2569

Edited: I think the best solution in this case, is use this third package django-annoying
This packaged contains a lot of syntactic sugar for things like that.

With this package, you can use the function get_object_or_None, similar to get_object_or_404.

But, the real code behind this function is :

def get_object_or_None(klass, *args, **kwargs):
    """
    Uses get() to return an object or None if the object does not exist.
    klass may be a Model, Manager, or QuerySet object. All other passed
    arguments and keyword arguments are used in the get() query.
    Note: Like with get(), a MultipleObjectsReturned will be raised if more than one
    object is found.
    """
    queryset = _get_queryset(klass)
    try:
        return queryset.get(*args, **kwargs)
    except queryset.model.DoesNotExist:
        return None

Note: Don’t use this if all you want to do is determine if at least one result exists. It’s more efficient to use exists().

Upvotes: 1

Rahul Gupta
Rahul Gupta

Reputation: 47846

You can use .first() operation on a queryset to your advantage to get the first object of the queryset if it exists and None otherwise.

Returns the first object matched by the queryset, or None if there is no matching object.

my_object = some_queryset.first() # return a object or 'None'

This will return the first object of the queryset if there are objects in the queryset. Otherwise, it returns None. It will automatically handle the case when objects do no exist without you needing to write try-except.

The above code is equivalent to writing:

try:
    my_object = some_queryset[0] # access the first element
except IndexError:
    my_object = None

Note: Here, we needed the object, so we are using .first(). If we needed to check only if the object exists, then we could have used .exists()

Upvotes: 1

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