Django. How can I render a class method?

Question

I apologize for the stupid question. This is my very first experience with OOP.

• Question 1: How can I render the value, which is calculated in my class method fseries(self)? I understand that the problem is with parenthesis. I have a number of similar calculated values, which need to be rendered. Shall I calculate / define all these values in class methods or somehow else?
• Question 2: Is it correct that I am getting the object via get_object_or_404(afc_series, valuefg = self.series) or shall I use another construction?

#views.py
...
    myfilter = Ksf_filter(name="mysuperfilter_XXX", series="ABCDE")
    #just testing correctness
    print(myfilter.name)
    print(myfilter.fseries())
    print(myfilter.fseries().valueecp)
    context = {'myfilter':myfilter,}
    return render(request, 'af/size/01_kss_size2.html', context)

#ksf_filter.py
from af.models import afc_series
from django.shortcuts import  get_object_or_404

class Ksf_filter:
    def __init__(self, name, series):
        self.name = name
        self.series = series

    def fseries(self):
        return get_object_or_404(afc_series, valuefg = self.series)

#template.html
{{myfilter.name}} ///// {{myfilter.fseries()}} //// {{myfilter.fseries().valueecp}})

This is the error message, I get.

#Error_msg  
TemplateSyntaxError at /ru/af/n01_size_kss/
Could not parse the remainder: '()' from 'myfilter.fseries()'
Request Method:     POST
Request URL:    http://127.0.0.1:5000/ru/af/n01_size_kss/
Django Version:     3.0.5
Exception Type:     TemplateSyntaxError
Exception Value:    
Could not parse the remainder: '()' from 'myfilter.fseries()'

Thank you

Answer 1

Django template variables automatically call a callable without extra parameters. So you can render this with:

{{ myfilter.fseries }} {{ myfilter.fseries.valueecp }}

The Django template language is deliberately restricted to do more advanced function calls to prevent people from writing business logic in the templates.

In case you need more advanced processing, you normally do this in the view. You can also use more extended template language like Jinja.

Question 2: Is it correct that I am getting the object via get_object_or_404(afc_series, valuefg = self.series) or shall I use another construction?

If valuefg is unique, then this can be used as an "identifier". Using get_object_or_404 is then a good idea, since it returns a 404 in case it can not find the element. You however should make sure that there is (at most) one value that can match.