Author: John Au-Yeung

Sometimes, we want to select only rows with duplicate field values with Python Django.

In this article, we’ll look at how to select only rows with duplicate field values with Python Django.

How to select only rows with duplicate field values with Python Django?

To select only rows with duplicate field values with Python Django, we can use the filter method.

For instance, we write

from django.db.models import Count

Literal.objects.values('name')
               .annotate(Count('id')) 
               .order_by()
               .filter(id__count__gt=1)

to call annotate with Count('id') to aggregate the rows with the same id value.

And then we call filter with the id__count__gt set to 1 to get the aggregate rows with the id count larger than 1.

Conclusion

To select only rows with duplicate field values with Python Django, we can use the filter method.

Sometimes, we want to add a page redirect with Python Django.

In this article, we’ll look at how to add a page redirect with Python Django.

How to add a page redirect with Python Django?

To add a page redirect with Python Django, we can add a RedirectView.

For instance, we write

from django.views.generic import RedirectView

urlpatterns = patterns('',
    (r'^one/$', RedirectView.as_view(url='/another/')),
)

to create a RedirectView by calling RedirectView.as_view with the url argument set to the URL we want to redirect to.

Conclusion

To add a page redirect with Python Django, we can add a RedirectView.

Sometimes, we want to add a placeholder on a CharField in Python Django.

In this article, we’ll look at how to add a placeholder on a CharField in Python Django.

How to add a placeholder on a CharField in Python Django?

To add a placeholder on a CharField in Python Django, we can use the forms.CharField class.

For instance, we write

q = forms.CharField(label='search', 
                    widget=forms.TextInput(attrs={'placeholder': 'Search'}))

in our form class to create the q CharField.

We set the placeholder of the CharField by setting the attrs argument to {'placeholder': 'Search'}.

Conclusion

To add a placeholder on a CharField in Python Django, we can use the forms.CharField class.

Sometimes, we want to check if a user is logged in with Python Django.

In this article, we’ll look at how to check if a user is logged in with Python Django.

How to check if a user is logged in with Python Django?

To check if a user is logged in with Python Django, we can use the request.user.is_authenticated property in our view.

For instance, in our view function, we write

if request.user.is_authenticated: 
    # ...

to check if the current user is authenticated with request.user.is_authenticated.

Conclusion

To check if a user is logged in with Python Django, we can use the request.user.is_authenticated property in our view.

Sometimes, we want to fix Python Django gives Bad Request (400) when DEBUG = False.

In this article, we’ll look at how to fix Python Django gives Bad Request (400) when DEBUG = False.

How to fix Python Django gives Bad Request (400) when DEBUG = False?

To fix Python Django gives Bad Request (400) when DEBUG = False, we set the ALLOWED_HOSTS setting to allow the hosts we want.

For instance, we write

ALLOWED_HOSTS = ['127.0.0.1', 'localhost']

to set the ALLOWED_HOSTS setting to an array of hosts that we allow to access our app.

We can allow all hosts with

ALLOWED_HOSTS = ['*']

Conclusion

To fix Python Django gives Bad Request (400) when DEBUG = False, we set the ALLOWED_HOSTS setting to allow the hosts we want.