How to filter queries over list of strings?

Question

I have a little problem.

I have a model Person and a list: fields=['firstname', 'age'].

Now, I would like to iterate over the fields list and do something like this:

people = Person.objects.all() #this is just to start
people_filtered = people.filter(firstname__icontains='ohn')

I am aware of a method

f = Person._meta.get_field('firstname') 

and that returns me an instance of a field

<django.db.models.fields.CharField: firstname>

but putting it like this:

people.filter(f__icontains='ohn')

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 667, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 685, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1259, in add_q
    can_reuse=used_aliases, force_having=force_having)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1127, in add_filter
process_extras=process_extras)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1325, in setup_joins
    "Choices are: %s" % (name, ", ".join(names)))
FieldError: Cannot resolve keyword 'f' into field. Choices are: age, firstname, id, lastname

How from this field get the result with '__icontains' I am hoping for?

class Person(models.Model):
    firstname = models.CharField(null=False, blank=False, max_length=32)
    lastname = models.CharField(null=False, blank=False, max_length=32)
    age = models.IntegerField(null=False, blank=False, max_length=8)

Answer 1

What list of string are you referring to? List of potential values or list of filters/arguments?

If you want the keywords/filters to be dynamic, then doing something like

key = '%s__icontains' % firstname

people.filter(**{key:'ohn'})

should work

If you want values to be dynamic, then this might work:

values = ['ohn', 'john', 'doe']

people.filter(firstname__icontains__in = values)

Im not sure if you can chain sql functions like icontains and in like that, but perhaps you can. I'm sure we are not first who have thought about this