Django : Why is string condition False if select_related field not coated in STR()?

Asked Apr 26 '22 at 10:05

Active Apr 26 '22 at 10:05

Viewed 37 times

In my function, my query is :

 mappings = MappingField.objects.filter(
        fl_fiche_header_flow_id=fhf.pk).order_by('fl_fiche_inside_field_position')
            .select_related('fl_fiche_header_flow')

Why when I print (label is models.Charfield):

mapping.fl_fiche_header_flow.label

I got well : appli1

And when I check the condition :

if mapping.fl_fiche_header_flow.label == 'appli1':

I obtain False?

Why do I need to str(mapping.fl_fiche_header_flow.label) in my condition for getting true?

Is it only due to select_related or is it a general principle ?

asked Apr 26 '22 at 10:05

Abpostman1

2

Because `.label` is not a string, but likely a `Label` object or something similar... – Willem Van Onsem Apr 26 '22 at 10:07
It seems to be a string. Because when I `print(mapping.fl_fiche_header_flow.label)`, the result is 'appli1' . That's the reason of my question. – Abpostman1 Apr 26 '22 at 10:21
1

And what do you get if you do `print(type(mapping.fl_fiche_header_flow.label))`? – solarissmoke Apr 26 '22 at 10:22
1

@Abpostman1: if you `print(..)` it calls `str(..)` on the item, and prints that content... – Willem Van Onsem Apr 26 '22 at 10:23
@Abpostman1: there is a difference between an object that `str(..)`s to `'x'` and the string `'x'`. – Willem Van Onsem Apr 26 '22 at 10:29
@solarissmoke: Exact: it's an object type : ``. @Willem Van Onsem : thanks for the tip. I didn't know this. Thanks – Abpostman1 Apr 26 '22 at 10:34

Django : Why is string condition False if select_related field not coated in STR()?

0 Answers0