Using a string as the argument to a Django filter query

Question

I'm trying to do a django query, but with the possibility of several different WHERE parameters. So I was thinking of doing something like:

querystring = "subcat__id__in=[1,3,5]"
Listing.objects.filter(querystring)

Here Listing is defined in my model, and it contains the Many-To-Many field subcat. However, that raises a ValueError because filter doesn't accept a string as its argument. Is there a way in Python to have a string evaluated as just its contents rather than as a string? Something like a print statement that prints the value of the string inline rather than to the standard output.

By the way, the reason I don't just do

querystring = [1,3,5]
Listing.objects.filter(subcat__id__in=querystring)

is that I'm not always filtering for subcat__id, sometimes it's one or several other parameters, and I'd rather not have to write out a bunch of separate queries controlled by if statements. Any advice is much appreciated.

Josh Smeaton · Accepted Answer · 2010-11-28 00:56:56Z

82

Perhaps...

filter_dict = {'subcat__id__in': [1,3,5]}
Listing.objects.filter(**filter_dict)

answered Nov 28, 2010 at 0:56

Josh Smeaton

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2 Comments

Josh Smeaton Over a year ago

@danny Accepted answer then? =P

Pramod Jangam Over a year ago

Is it possible to do or using this pattern. e.g. Q(subcat__id__in =[1,3,5]) | Q(cat__id=9)?

Ignacio Vazquez-Abrams · Accepted Answer · 2010-11-28 00:56:43Z

9

Listing.objects.filter(**{"subcat__id__in": ast.literal_eval("[1,3,5]")})

answered Nov 28, 2010 at 0:56

Ignacio Vazquez-Abrams

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Comments

Alexandre Norman · Accepted Answer · 2023-06-14 09:56:00Z

1

You can do an OR query like this:

from functools import reduce
from operator import or_

query_as_dict = {"subcat__id__in": [1,3,5], "cat__id": 9}
query = reduce(or_, (Q(**{key: value}) for key, value in query_as_dict.items()))
Listing.objects.filter(query)

answered Jun 14, 2023 at 9:56

Alexandre Norman

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