Building query string with form fields

Question

I have a form which sends some parameters to a view where I use this parameters as a filter in a query. The search parameters are not obligatory and when a field of the form is left blank, I do not use it as a filter criteria.

I was trying to create the string for the query but get an error: "too many values to unpack"

Any Ideas of what could be happening? Also any ideas of a simpler way to do it would also be appreciated!

My view is like this (in the dict busca, the keys are form names and values database fields as django model)

def index(request):

a={}
busca={'marca':'brand = ', 'modelo':'model = ', 'tamano_min':'size >= '}
for i in request.POST:
    if i in ['marca', 'modelo', 'tamano_min']:
        valor=request.POST.get(i)
        a[i]=str.join(busca[i], valor)

query=list(a.values)
query=' and '.join(query)
latest_products = products.objects.filter(query, )

template = loader.get_template('search/index.html')
context = {'latest_products': latest_products}
return render(request, 'search/index.html', context)

alecxe · Accepted Answer · 2014-05-08 13:43:59Z

2

Don't reinvent the wheel by constructing your own query and use the power of Django ORM.

For example:

marca = request.POST.get('marca')
modelo = request.POST.get('modelo')
tamano_min = request.POST.get('tamano_min')

latest_products = products.objects.filter(brand=marca, model=modelo, size__gte=tamano_min)

get() helps to get the value of POST parameter or None if no parameter found in the dictionary.
__gte ending helps to add >= condition.

You may also want to check marca, modelo and tamano_min before using them:

latest_products = products.objects.all()
if marca is not None:
    latest_products = latest_products.filter(brand=marca)

And so on.

edited May 8, 2014 at 13:43

answered May 8, 2014 at 13:37

alecxe

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5 Comments

user2950162 Over a year ago

the issue is when one of those fields are left empty... if I have brand="" it will return the ones with no brand instead of all brands... also what the_gte after size means? thanks for the help!

user2950162 Over a year ago

I can check it before, but in case it is non existent, can I use something like brand=* to select all brands? otherwise I have the same problem because I have brand=marca and if marca is non existent I still have it in my query... and thanks again!

alecxe Over a year ago

@user2950162 this is what if already does here. If you don't include brand= condition, you'll get all brands. See, you first make latest_products = products.objects.all(), then add filters on it.

user2950162 Over a year ago

so I would get all and then filter for each parameter like you did for marca?

alecxe Over a year ago

@user2950162 yup, and since django querysets are "lazy" it wouldn't make an actual query to the database until iterated over or evaluated.

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