Question 184121 in Html Question posted in
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Html – Sum of values ​in Django views

I intend to make a query to get a value and then add that value to 1 in the django views, but when I try to do that, I always get an error

def atualizar(request, contador):
        
        lista = factura.objects.filter(contador__contador=contador)
        conta1 = factura.objects.filter(contador__contador=contador).order_by('-contar')[:1]
        conta=conta1.values('contar') # this is value 
        cont=cliente.objects.filter(contador=contador).first() 
        if request.POST:
            
            data1=request.POST['data1']
            factura_nr=request.POST['factura_nr']
            data2=request.POST['data2']
            consumo=request.POST['consumo']
            
            dados = factura(
                contador=cont, 
                contar= conta +1, # to incremet here
                consumo=consumo,
                data1=data1,
                data2=data2,
                factura_nr=factura_nr

            )
            dados.save()
        
        return render(request, 'tabela.html', {'lista': lista,'cont':cont ,'conta':conta})[enter image description here](https://i.stack.imgur.com/BdaMk.png)
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2

Answers


  1. 0

    updated:
    values() returns a Queryset that behaves similar to a dict. Simply try

    =conta1['contar'] + 1
or
=conta[0]['contar']

    to debug print(conta) and you will see it

    please add the error trace in future posts

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  2. 0

    You can determine the maximum contar and then increment this with one, like:

    from django.db.models import Max


def atualizar(request, contador):
    lista = factura.objects.filter(contador__contador=contador)
    conta = lista.aggregate(max_contar=Max('contar'))['max_contar'] or 0
    cont = get_object_or_404(cliente, contador=contador)
    if request.method == 'POST':
        data1 = request.POST['data1']
        factura_nr = request.POST['factura_nr']
        data2 = request.POST['data2']
        consumo = request.POST['consumo']
        dados = factura.objects.create(
            contador=cont,
            contar=conta + 1,  # to incremet here
            consumo=consumo,
            data1=data1,
            data2=data2,
            factura_nr=factura_nr,
        )
        return redirect('name-of-some-view')

    return render(
        request, 'tabela.html', {'lista': lista, 'cont': cont, 'conta': conta}
    )

    Note: Models in Django are written in PascalCase, not snake_case,
    so you might want to rename the model from factura to Factura.

    Note: It is better to use a Form [Django-doc]
    than to perform manual validation and cleaning of the data. A Form will not
    only simplify rendering a form in HTML, but it also makes it more convenient
    to validate the input, and clean the data to a more convenient type.

    Note: It is often better to use get_object_or_404(…) [Django-doc],
    then to use .get(…) [Django-doc] directly. In case the object does not exists,
    for example because the user altered the URL themselves, the get_object_or_404(…) will result in returning a HTTP 404 Not Found response, whereas using
    .get(…) will result in a HTTP 500 Server Error.

    Note: In case of a successful POST request, you should make a redirect
    [Django-doc]
    to implement the Post/Redirect/Get pattern [wiki].
    This avoids that you make the same POST request when the user refreshes the
    browser.

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