Building Custom Query Filters Lists in Django

Question

I'm building my filters as a list but having trouble building them with the Q function. It seems to be that doing things manually the filters work but when trying to build up the filters by concatenating strings I get the following issues:

Here is the Query:

MyLocationFilter = BuildQueryORFilter('MyLocationCountryCode', MyLocationCodePref1)
list = AboutMe.objects.order_by('MyLinkedInLastName').filter(reduce(OR, MyLocationFilter))

And here is how I am building those Filters:

def BuildQueryORFilter(fieldname, fieldvalues):
    QueryList = []
    spltfieldvalues = fieldvalues.split()
    for item in spltfieldvalues:
        strpitem = item.strip('[],')
        queryitem = Q(fieldname+"__contains="+strpitem)
        QueryList.append(queryitem)
    return QueryList

However the problem seems to be how to get Q(..) in the form of Q(fieldname__contains=gb) rather than Q('fieldname__contains=gb') which seems to be throwing up issues such as:

ValueError
Exception Value:    
need more than 1 value to unpack

How should I build the Q queries to avoid this unpacking issue?

Traceback for possible answer (below)

Traceback:
File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/home/brett/LinkedIn/phaseone/jelt/views.py" in AboutMeList
  259.  list = AboutMe.objects.order_by('MyLinkedInLastName').filter(MyLocationFilter)
File "/usr/lib/python2.7/dist-packages/django/db/models/query.py" in filter
  624.         return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/lib/python2.7/dist-packages/django/db/models/query.py" in _filter_or_exclude
  642.             clone.query.add_q(Q(*args, **kwargs))
File "/usr/lib/python2.7/dist-packages/django/db/models/sql/query.py" in add_q
  1250.                             can_reuse=used_aliases, force_having=force_having)
File "/usr/lib/python2.7/dist-packages/django/db/models/sql/query.py" in add_filter
  1056.         arg, value = filter_expr

Exception Type: ValueError at /list/
Exception Value: need more than 1 value to unpack

Alasdair · Accepted Answer · 2013-09-21 17:06:37Z

2

Pass the keyword argument by unpacking a dict.

    strpitem = item.strip('[],')
    key = fieldname + "__contains"
    d = {key: strpitem}
    queryitem = Q(**d)

edited Sep 21, 2013 at 17:06

answered Sep 21, 2013 at 15:36

Alasdair

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10 Comments

disruptive Over a year ago

I tied this, but when printing out queryitem to screen I get: (AND: ('MyLocationCountryCode__contains', u'gb')) and I'm still getting the same issue when trying to filter.

Alasdair Over a year ago

Is that the traceback when you use the answer I suggested? What is the result of printing the dictionary d? There might be a typo in my suggestion, or another mistake in your question that I haven't spotted, but it's definitely closer to the correct solution. It is not possible to pass a single string argument toQ().

disruptive Over a year ago

printing the dictionary: Content-Type: text/html; charset=utf-8 {'MyLocationCountryCode__contains': u'gb'}

disruptive Over a year ago

I can't seem to find a smart way to unpack that dictionary

Alasdair Over a year ago

I can't spot any other bugs. I would start with something really basic like d={'MyLocationCountryCode__contains': 'gb'} and AboutMe.objects.filter(Q(**d)), then build up the functionality of your method from there. Good luck!

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