Django view: Count specific value from model

Question

In a django view I have:

 signed_by = Demographic.objects.all().values_list('data_entered_by')

And I get [(u'Patient',),(u'Patient',), (u'Other',)].

I want to count all that have Patient value and all that have Other value respectively.

In case I use

signed_by.count()

I get the count for all. How do I count a specified value?

AKS · Accepted Answer · 2016-05-17 12:03:10Z

2

You can annotate the queryset:

signed_by = Demographic.objects.values('data_entered_by').annotate(cnt=Count('id'))

As a result you can get count for each data_entered_by value as follows, since it return a list of dict object:

for q in signed_by:
    print(q['data_entered_by'], q['cnt])

From the documentation:

When an annotate() clause is specified, each object in the QuerySet will be annotated with the specified values.

edited May 17, 2016 at 12:03

answered May 17, 2016 at 11:34

AKS

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6 Comments

zinon Over a year ago

What is the meaning of the annotate()?

zinon Over a year ago

I want to get a number for each.

AKS Over a year ago

I added what annotate does. It is used to annotate each object in a queryset with certain computed fields. I don't understand this part from your comments though ... I want to get a number for each ?

zinon Over a year ago

And I case I want to print the cnt value for each of them, how will I do it?

zinon Over a year ago

OK, great! Thanks! You answer is really helpful!

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