Python 带有或条件的Django筛选器使用dict参数

我在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。因为它是一个函数，所以它必须是通用的。因此，为了使其可重用，我将dict作为参数传递给

filter

和

exclude

操作。这就是功能：

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

如果我用一个简单的dict（如

{'title'：'foo'，'name'：'bar}

过滤查询集，效果会非常好。然而，情况并非总是如此。我需要使用

django.db.models.Q

实用程序对需要

或

条件的更复杂查询执行筛选

---

那么，如何将这些参数作为字典传递给过滤器呢。有什么方法可以做到这一点吗？

您可以将您的字典重新构造为一个单键值字典列表，并在

Q

表达式中的每个

dict

上使用解包，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

on

或

将

Q

表达式连接到or上

您还可以使用生成器表达式，其中包含

dict

s的

list

：

q = model.objects.filter(reduce(operator.or_, 
                                (Q(**d) for d in (dict([i]) for i in my_filter.items()))))

---

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'))

记住这一点，您可能希望将存储在

my_filter

中的所有查询加载到

Q

对象中。然后，您可以通过上面的相同方法，通过按位

和
连接所有非OR查询：
根据@Moses Koledoye的回答，我可以解决这个问题。这就是我的函数现在的样子：

 cached_query(key, model, my_filter=None, or_filter={}, 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 or_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:
        result = model.objects.all()
        if my_filter:
            result = model.objects.filter(**my_filter)
        if or_filter:
            reduced_filter = reduce(operator.or_, (Q(**d) for d in [dict([i]) for i in or_filter.items()]))
            result = result.filter(reduced_filter)
        if exclude:
            result = result.exclude(**exclude)
        if order_by:
            result = result.order_by(*order_by)
        result = result[:sliced]
        cache.set(key, result, cache_timeout)
    return result

哎呀，在引号里有一个项目。如上所述。