我在我的Django应用程序上有一个函数,我在其中执行一些Queryset操作并将其结果设置为Memcache。由于它是一种功能,因此必须具有一般用途。因此,为了使其可重复使用,我将dict作为filter
和exclude
操作的参数传递。这是功能:
def cached_query(key, model, my_filter=None, exclude=None, order_by=None, sliced=50):
"""
:param key: string used as key reference to store on Memcached
:param model: model reference on which 'filter' will be called
:param my_filter: dictionary containing the filter parameters (eg.: {'title': 'foo', 'category': 'bar'}
:param sliced: integer limit of results from the query. The lower the better, since for some reason Django Memcached
won't store thousands of entries in memory
:param exclude: dictionary containing the exclude parameters (eg.: {'title': 'foo', 'category': 'bar'}
:param order_by: tuple containing the list of fields upon which the model will be ordered.
:return: list of models. Not a QuerySet, since it was sliced.
"""
result = cache.get(key, None)
if not result:
if my_filter:
result = model.objects.filter(**my_filter)
if exclude:
result = result.exclude(**exclude)
if order_by:
result = result.order_by(*order_by)
else:
result = model.objects.all()
result = result[:sliced]
cache.set(key, result, cache_timeout)
return result
如果我使用像{'title': 'foo', 'name': 'bar'}
这样的简单dict过滤查询集,它的工作原理非常好。然而,并非总是如此。我需要使用django.db.models.Q
实用程序执行过滤器,以处理需要OR
条件的更复杂查询。
那么,我如何将这些参数作为字典传递给过滤器。对此有什么办法吗?
答案 0 :(得分:8)
您可以将字典重组为单个键值字典列表,并在dict
表达式中的每个Q
上使用解压缩,如下所示:
from functools import reduce
import operator
from django.db.models import Q
# your dict is my_filter
q = model.objects.filter(reduce(operator.or_,
(Q(**d) for d in [dict([i]) for i in my_filter.items()])))
reduce
上的 or_
在OR上加入Q
个表达式。
您还可以使用生成器表达式,其中list
为dict
:
q = model.objects.filter(reduce(operator.or_,
(Q(**d) for d in (dict([i]) for i in my_filter.items()))))
答案 1 :(得分:4)
您可以使用按位|
运算符。
my_filter = Q()
# Or the Q object with the ones remaining in the list
my_or_filters = {'some_field__gte':3.5, 'another_field':'Dick Perch'}
for item in my_or_filters:
my_filter |= Q(**{item:my_or_filters[item]})
model.objects.filter(my_filter)
# unpacks to model.objects.filter(Q(some_field__gte=3.5) | Q(another_field='Dick Perch'))
考虑到这一点,您可能希望将my_filter
中存储的所有查询加载到Q
个对象中。然后,您可以通过上面使用按位&
的相同方法加入所有非OR查询:
my_filter& = ...
答案 2 :(得分:0)
根据@Moses Koledoye的回答,我可以解决这个问题。这就是我现在的功能:
{{1}}