Constructing Django filter queries dynamically with args and kwargs

Question

I'm constructing some Django filter queries dynamically, using this example:

kwargs = { 'deleted_datetime__isnull': True }
args = ( Q( title__icontains = 'Foo' ) | Q( title__icontains = 'Bar' ) )
entries = Entry.objects.filter( *args, **kwargs )

I'm just not sure how to construct the entry for args. Say I have this array:

strings = ['Foo', 'Bar']

How do I get from there to:

args = ( Q( title__icontains = 'Foo' ) | Q( title__icontains = 'Bar' )

The closest I can get is:

for s in strings:
    q_construct = Q( title__icontains = %s) % s
    args.append(s)

But I don't know how to set up the | condition.

Roshan · Accepted Answer · 2013-04-07 06:40:30Z

14

you have list of Q class objects,

args_list = [Q1,Q2,Q3]   # Q1 = Q(title__icontains='Foo') or Q1 = Q(**{'title':'value'})  
args = Q()  #defining args as empty Q class object to handle empty args_list
for each_args in args_list :
    args = args | each_args

query_set= query_set.filter(*(args,) ) # will excute, query_set.filter(Q1 | Q2 | Q3)
# comma , in last after args is mandatory to pass as args here

answered Apr 7, 2013 at 6:40

Roshan

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2 Comments

Alex78191 Over a year ago

why not args |= each_args?

Roshan Over a year ago

Thanks for suggestion. I will write enhance this answer. :)

j_syk · Accepted Answer · 2011-12-14 19:21:09Z

13

You can iterate it directly using a kwarg format (I don't know the proper term)

argument_list = [] #keep this blank, just decalring it for later
fields = ('title') #any fields in your model you'd like to search against
query_string = 'Foo Bar' #search terms, you'll probably populate this from some source

for query in query_string.split(' '):  #breaks query_string into 'Foo' and 'Bar'
    for field in fields:
        argument_list.append( Q(**{field+'__icontains':query_object} ) ) 

query = Entry.objects.filter( reduce(operator.or_, argument_list) )

# --UPDATE-- here's an args example for completeness

order = ['publish_date','title'] #create a list, possibly from GET or POST data
ordered_query = query.order_by(*orders()) # Yay, you're ordered now!

This will look for each string in your query_string in each field in fields and OR the result

I wish I still had my original source for this, but this is adapted from code I use.

edited Dec 14, 2011 at 19:21

answered Dec 14, 2011 at 19:07

j_syk

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1 Comment

wasabigeek Over a year ago

on a side note, reduce is now functools.reduce in Python 3 docs.python.org/3.0/library/functools.html#functools.reduce

Ryan · Accepted Answer · 2018-10-16 04:21:12Z

1

firstQ = [
    Q(...),
    Q(...),
    Q(...)
]
import functools
functools.reduce(lambda a, b: a & b, Qrelationship)

Or in my case, I needed to AND to different sets of filters:

firstQ = [
    Q(...),
    Q(...),
    Q(...)
]
secondQ = [
    Q(...),
    Q(...),
    Q(...)
]
import functools
combined = functools.reduce(lambda a, b: a | b, [
    functools.reduce(lambda a, b: a & b, firstQ),
    functools.reduce(lambda a, b: a & b, secondQ)
])
myqueryset = Model.objects.filter(combined)
# Make sure you apply the Q's first (BEFORE any other filter) or it will fail silently

answered Oct 16, 2018 at 4:21

Ryan

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