在Python类中序列化@property方法

Question

有没有办法在序列化Django模型类时将任何@property定义传递给json序列化程序？

例:

class FooBar(object.Model)

    name = models.CharField(...)

    @property
    def foo(self):
        return "My name is %s" %self.name

想序列化为:

[{

    'name' : 'Test User',

    'foo' : 'My name is Test User',
},]

Answer 1

您可以在没有/太多工作的情况下扩展Django的序列化程序.这是一个自定义序列化程序,它接受一个查询集和一个属性列表(字段与否),并返回JSON.

from StringIO import StringIO
from django.core.serializers.json import Serializer

class MySerializer(Serializer):
    def serialize(self, queryset, list_of_attributes, **options):
        self.options = options
        self.stream = options.get("stream", StringIO())
        self.start_serialization()
        for obj in queryset:
            self.start_object(obj)
            for field in list_of_attributes:
                self.handle_field(obj, field)
            self.end_object(obj)
        self.end_serialization()
        return self.getvalue()

    def handle_field(self, obj, field):
        self._current[field] = getattr(obj, field)

用法:

>>> MySerializer().serialize(MyModel.objects.all(), ["field1", "property2", ...])

当然,这可能比编写自己更简单的JSON序列化程序更有用,但可能没有比自己的XML序列化程序更多的工作(除了将基类更改为以外,您还必须重新定义"handle_field"以匹配XML案例.去做).

Answer 2

这个解决方案效果很好,由M. Rafay Aleem和Wtower提出,但它是重复的代码.这是一个改进:

from django.core.serializers.base import Serializer as BaseSerializer
from django.core.serializers.python import Serializer as PythonSerializer
from django.core.serializers.json import Serializer as JsonSerializer

class ExtBaseSerializer(BaseSerializer):

    def serialize_property(self, obj):
        model = type(obj)
        for field in self.selected_fields:
            if hasattr(model, field) and type(getattr(model, field)) == property:
                self.handle_prop(obj, field)

    def handle_prop(self, obj, field):
        self._current[field] = getattr(obj, field)

    def end_object(self, obj):
        self.serialize_property(obj)

        super(ExtBaseSerializer, self).end_object(obj)


class ExtPythonSerializer(ExtBaseSerializer, PythonSerializer):
    pass


class ExtJsonSerializer(ExtPythonSerializer, JsonSerializer):
    pass

如何使用它:

ExtJsonSerializer().serialize(MyModel.objects.all(), fields=['field_name_1', 'property_1' ...])

Answer 3

自2010年以来,情况发生了一些变化,因此@ user85461的答案似乎不再适用于Django 1.8和Python 3.4.这是一个更新的答案,似乎对我有用.

from django.core.serializers.base import Serializer as BaseSerializer
from django.core.serializers.python import Serializer as PythonSerializer
from django.core.serializers.json import Serializer as JsonSerializer
from django.utils import six

class ExtBaseSerializer(BaseSerializer):
    """ Abstract serializer class; everything is the same as Django's base except from the marked lines """
    def serialize(self, queryset, **options):
        self.options = options

        self.stream = options.pop('stream', six.StringIO())
        self.selected_fields = options.pop('fields', None)
        self.selected_props = options.pop('props', None)  # added this
        self.use_natural_keys = options.pop('use_natural_keys', False)
        self.use_natural_foreign_keys = options.pop('use_natural_foreign_keys', False)
        self.use_natural_primary_keys = options.pop('use_natural_primary_keys', False)

        self.start_serialization()
        self.first = True
        for obj in queryset:
            self.start_object(obj)
            concrete_model = obj._meta.concrete_model
            for field in concrete_model._meta.local_fields:
                if field.serialize:
                    if field.rel is None:
                        if self.selected_fields is None or field.attname in self.selected_fields:
                            self.handle_field(obj, field)
                    else:
                        if self.selected_fields is None or field.attname[:-3] in self.selected_fields:
                            self.handle_fk_field(obj, field)
            for field in concrete_model._meta.many_to_many:
                if field.serialize:
                    if self.selected_fields is None or field.attname in self.selected_fields:
                        self.handle_m2m_field(obj, field)
            # added this loop
            if self.selected_props:
                for field in self.selected_props:
                    self.handle_prop(obj, field)
            self.end_object(obj)
            if self.first:
                self.first = False
        self.end_serialization()
        return self.getvalue()

    # added this function
    def handle_prop(self, obj, field):
        self._current[field] = getattr(obj, field)


class ExtPythonSerializer(ExtBaseSerializer, PythonSerializer):
    pass


class ExtJsonSerializer(ExtPythonSerializer, JsonSerializer):
    pass

用法:

>>> ExtJsonSerializer().serialize(MyModel.objects.all(), fields=['myfield', ...], props=['myprop', ...])

Answer 4

这是M. Rafay Aleem和Wtowers的回答和嘲讽的结合。这是DRY，只能让您指定额外的道具，而不是像caots版本中那样指定所有字段和道具。

from django.core.serializers.json import Serializer as JsonSerializer
from django.core.serializers.python import Serializer as PythonSerializer
from django.core.serializers.base import Serializer as BaseSerializer

class ExtBaseSerializer(BaseSerializer):
    def serialize(self, queryset, **options):
        self.selected_props = options.pop('props')
        return super(ExtBaseSerializer, self).serialize(queryset, **options)

    def serialize_property(self, obj):
        model = type(obj)
        for field in self.selected_props:
            if hasattr(model, field) and type(getattr(model, field)) == property:
                self.handle_prop(obj, field)

    def handle_prop(self, obj, field):
        self._current[field] = getattr(obj, field)

    def end_object(self, obj):
        self.serialize_property(obj)

        super(ExtBaseSerializer, self).end_object(obj)

class ExtPythonSerializer(ExtBaseSerializer, PythonSerializer):
    pass

class ExtJsonSerializer(ExtPythonSerializer, JsonSerializer):
    pass

如何使用它：

ExtJsonSerializer().serialize(MyModel.objects.all(), props=['property_1', ...])

Answer 5

您可以使用一些黑魔法来获取类的所有属性：

def list_class_properties(cls):
    return [k for k,v in cls.__dict__.iteritems() if type(v) is property]

例如：

>>> class Foo:
       @property
       def bar(self):
           return "bar"

>>> list_class_properties(Foo)
['bar']

然后您可以构建字典并从那里对其进行序列化。