django access queryset values code example

Example 1: query set

A QuerySet is a list of a dictionary of objects in your database.

Example 2: get_queryset django

They indeed do different things.

get()
This is a top-level method, and there's one for each HTTP verb - get(), post(), patch(), etc. You would override it when you want to do something before a request is processed by the view, or after. But this is only called when a form view is loaded for the first time, not when the form is submitted. Basic example in the documentation. By default it will just render the configured template and return the HTML.

class MyView(TemplateView):
    # ... other methods

    def get(self, *args, **kwargs):
        print('Processing GET request')
        resp = super().get(*args, **kwargs)
        print('Finished processing GET request')
        return resp
get_queryset()
Used by ListViews - it determines the list of objects that you want to display. By default, it will just give you all for the model you specify. By overriding this method you can extend or completely replace this logic. Django documentation on the subject.

class FilteredAuthorView(ListView):
    template_name = 'authors.html'
    model = Author

    def get_queryset(self):
        # original qs
        qs = super().get_queryset() 
        # filter by a variable captured from url, for example
        return qs.filter(name__startswith=self.kwargs['name'])
get_context_data()
This method is used to populate a dictionary to use as the template context. For example, ListViews will populate the result from get_queryset() as author_list in the above example. You will probably be overriding this method most often to add things to display in your templates.

def get_context_data(self, **kwargs):
    data = super().get_context_data(**kwargs)
    data['page_title'] = 'Authors'
    return data
And then in your template, you can reference these variables.

<h1>{{ page_title }}</h1>

<ul>
{% for author in author_list %}
    <li>{{ author.name }}</li>
{% endfor %}
</ul>
Now to answer your main question, the reason you have so many methods is to let you easily stick your custom logic with pin-point accuracy. It not only allows your code to be more readable and modular, but also more testable.

The documentation should explain everything. If still not enough, you may find the sources helpful as well. You'll see how everything is implemented with mixins which are only possible because everything is compartmentalized.

Example 3: get queryset

class PurchaseList(generics.ListAPIView):
    serializer_class = PurchaseSerializer

    def get_queryset(self):
        """
        Optionally restricts the returned purchases to a given user,
        by filtering against a `username` query parameter in the URL.
        """
        queryset = Purchase.objects.all()
        username = self.request.query_params.get('username', None)
        if username is not None:
            queryset = queryset.filter(purchaser__username=username)
        return queryset

Example 4: django filter values with OR operator

Blog.objects.filter(pk__in=[1, 4, 7])

Example 5: django filter values with e and operator

exact
iexact
contains
icontains
in
gt
gte
lt
lte
startswith
istartswith
endswith
iendswith
range

date
year
iso_year
month
day
week
week_day
iso_week_day
quarter
time
hour
minute
second

isnull
regex
iregex