如何从sqlalchemy中对象进行jsonify？ [英] How to jsonify objects from sqlalchemy?

问题描述

我正在使用Flask，SQLAlchemy和javascript。我需要通过AJAX将查询结果传递给json格式的javascript，但我一直收到此错误：

I'm using Flask, SQLAlchemy and javascript. I need to pass the results of my query to javascript in the json format, through AJAX, but I keep getting this error:

raise TypeError(repr(o) + " is not JSON serializable")
TypeError: <model.Cloud object at 0x7f72e40c5910> is not JSON serializable'

我的代码如下：

@app.route('/past/<user_id>')
def get_past_clouds(user_id):
    if user_id:
        clouds = model_session.query(model.User).filter_by(id=user_id).first().clouds
        if clouds != "":
            clouds_d = {}
            for idx, cloud in enumerate(clouds):
                clouds_d[idx] = cloud
            return jsonify(json_list=clouds_d)
    return None

忽略我之前的评论，允许请求生效但所有返回的对象都未定义。

Ignore my previous comment, that allowed the request to work but all the objects returned were undefined.

这就是我的看法最终做到了：

This is how I did it in the end:

clouds_d = dict( (cloud.name, [ photo.to_dict() for photo in cloud.photos ]) for cloud in clouds )
return jsonify(clouds_d)

推荐答案

正如您所发现的，SQLAlchemy模型不是本机的可以序列化为JSON。

As you’ve discovered, SQLAlchemy models are not natively serializable to JSON.

您采用的方法 - 从模型实例的属性手动构造dict - 完成工作，但如果您需要jsonify多个模型，请处理价值转换序列化，或支持反序列化（将JSON转换回SQLAlchemy模型实例），你会发现自己编写了大量繁琐的代码。

The approach you adopted - to manually construct a dict from your model instance’s properties - gets the job done, but if you need to jsonify multiple models, deal with value conversions on serialization, or support deserialization (converting JSON back to a SQLAlchemy model instance) you’ll find yourself writing a lot of tedious code.

更好的解决方案是使用序列化SQLAlchemy的/ deserialization扩展库，例如 SQLAthanor 或 Marshmallow-SQLAlchemy （完全披露：我是SQLAthanor的作者）。

A better solution is to use a serialization/deserialization extension library for SQLAlchemy, such as either SQLAthanor or Marshmallow-SQLAlchemy (full disclosure: I am the author of SQLAthanor).

使用这些库中的任何一个，您基本上可以将SQLAlchemy模型序列化和反序列化为其他格式，或者将它们反序列化为SQLAlchemy模型实例。

Using either of these libraries, you can basically serialize and deserialize SQLAlchemy models to other formats or deserialize them back into SQLAlchemy model instances.

对于SQLAthanor，您可以基本上得到使用一个方法调用完成的工作：

In the case of SQLAthanor, you can basically get the job done with one method call:

json_result = model_instance.dump_to_json()

或（使用更多配置可以提供更精细的控制）：

or (with some more configuration that gives you more fine-grained control):

json_result = model_instance.to_json()

您还可以序列化为dict ，或YAML或CSV。

You can also serialize to dict, or YAML, or CSV.

相反的过程是：

model_instance = ModelClass.new_from_json(json_result)

希望这会有所帮助！

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