[英]How to serialize SqlAlchemy result to JSON?
Django 对从 DB 返回的 ORM 模型自动序列化为 JSON 格式。
如何将SQLAlchemy查询结果序列化为JSON格式?
我试过jsonpickle.encode
但它本身对查询 object 进行编码。 我试过json.dumps(items)
但它返回
TypeError: <Product('3', 'some name', 'some desc')> is not JSON serializable
将 SQLAlchemy ORM 对象序列化为 JSON /XML 真的那么难吗? 它没有任何默认的序列化程序吗? 现在序列化 ORM 查询结果是很常见的任务。
我需要的只是返回 SQLAlchemy 查询结果的 JSON 或 XML 数据表示。
SQLAlchemy对象查询结果JSON/XML格式需要在javascript datagird(JQGrid http://www.trirand.com/blog/ )中使用
您可以将对象输出为字典:
class User:
def as_dict(self):
return {c.name: getattr(self, c.name) for c in self.__table__.columns}
然后你使用User.as_dict()
来序列化你的对象。
你可以使用这样的东西:
from sqlalchemy.ext.declarative import DeclarativeMeta
class AlchemyEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# an SQLAlchemy class
fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
data = obj.__getattribute__(field)
try:
json.dumps(data) # this will fail on non-encodable values, like other classes
fields[field] = data
except TypeError:
fields[field] = None
# a json-encodable dict
return fields
return json.JSONEncoder.default(self, obj)
然后使用以下方法转换为 JSON:
c = YourAlchemyClass()
print json.dumps(c, cls=AlchemyEncoder)
它将忽略不可编码的字段(将它们设置为“无”)。
它不会自动扩展关系(因为这可能导致自我引用,并永远循环)。
但是,如果您希望永远循环,则可以使用:
from sqlalchemy.ext.declarative import DeclarativeMeta
def new_alchemy_encoder():
_visited_objs = []
class AlchemyEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# don't re-visit self
if obj in _visited_objs:
return None
_visited_objs.append(obj)
# an SQLAlchemy class
fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
fields[field] = obj.__getattribute__(field)
# a json-encodable dict
return fields
return json.JSONEncoder.default(self, obj)
return AlchemyEncoder
然后使用以下方法对对象进行编码:
print json.dumps(e, cls=new_alchemy_encoder(), check_circular=False)
这将编码所有的孩子,他们所有的孩子,还有他们所有的孩子......基本上可以对整个数据库进行编码。 当它到达之前编码的东西时,它会将其编码为“无”。
另一种可能更好的替代方法是能够指定要扩展的字段:
def new_alchemy_encoder(revisit_self = False, fields_to_expand = []):
_visited_objs = []
class AlchemyEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# don't re-visit self
if revisit_self:
if obj in _visited_objs:
return None
_visited_objs.append(obj)
# go through each field in this SQLalchemy class
fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
val = obj.__getattribute__(field)
# is this field another SQLalchemy object, or a list of SQLalchemy objects?
if isinstance(val.__class__, DeclarativeMeta) or (isinstance(val, list) and len(val) > 0 and isinstance(val[0].__class__, DeclarativeMeta)):
# unless we're expanding this field, stop here
if field not in fields_to_expand:
# not expanding this field: set it to None and continue
fields[field] = None
continue
fields[field] = val
# a json-encodable dict
return fields
return json.JSONEncoder.default(self, obj)
return AlchemyEncoder
您现在可以使用以下命令调用它:
print json.dumps(e, cls=new_alchemy_encoder(False, ['parents']), check_circular=False)
例如,仅扩展名为“parents”的 SQLAlchemy 字段。
from dataclasses import dataclass
from datetime import datetime
from flask import Flask, jsonify
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
db = SQLAlchemy(app)
@dataclass
class User(db.Model):
id: int
email: str
id = db.Column(db.Integer, primary_key=True, auto_increment=True)
email = db.Column(db.String(200), unique=True)
@app.route('/users/')
def users():
users = User.query.all()
return jsonify(users)
if __name__ == "__main__":
users = User(email="user1@gmail.com"), User(email="user2@gmail.com")
db.create_all()
db.session.add_all(users)
db.session.commit()
app.run()
/users/
路由现在将返回用户列表。
[
{"email": "user1@gmail.com", "id": 1},
{"email": "user2@gmail.com", "id": 2}
]
@dataclass
class Account(db.Model):
id: int
users: User
id = db.Column(db.Integer)
users = db.relationship(User) # User model would need a db.ForeignKey field
来自jsonify(account)
的响应是这样的。
{
"id":1,
"users":[
{
"email":"user1@gmail.com",
"id":1
},
{
"email":"user2@gmail.com",
"id":2
}
]
}
from flask.json import JSONEncoder
class CustomJSONEncoder(JSONEncoder):
"Add support for serializing timedeltas"
def default(o):
if type(o) == datetime.timedelta:
return str(o)
elif type(o) == datetime.datetime:
return o.isoformat()
else:
return super().default(o)
app.json_encoder = CustomJSONEncoder
您可以将 RowProxy 转换为这样的字典:
d = dict(row.items())
然后将其序列化为 JSON(您必须为诸如datetime
值之类的内容指定一个编码器)如果您只想要一条记录(而不是相关记录的完整层次结构),这并不难。
json.dumps([(dict(row.items())) for row in rs])
我建议使用棉花糖。 它允许您创建序列化程序来表示您的模型实例,并支持关系和嵌套对象。
这是他们文档中的一个截断示例。 以 ORM 模型为例, Author
:
class Author(db.Model):
id = db.Column(db.Integer, primary_key=True)
first = db.Column(db.String(80))
last = db.Column(db.String(80))
该类的棉花糖模式构造如下:
class AuthorSchema(Schema):
id = fields.Int(dump_only=True)
first = fields.Str()
last = fields.Str()
formatted_name = fields.Method("format_name", dump_only=True)
def format_name(self, author):
return "{}, {}".format(author.last, author.first)
...并像这样使用:
author_schema = AuthorSchema()
author_schema.dump(Author.query.first())
...会产生这样的输出:
{
"first": "Tim",
"formatted_name": "Peters, Tim",
"id": 1,
"last": "Peters"
}
看看他们完整的Flask-SQLAlchemy 示例。
一个名为marshmallow-sqlalchemy
库专门集成了 SQLAlchemy 和 marshmallow。 在该库中,上述Author
模型的架构如下所示:
class AuthorSchema(ModelSchema):
class Meta:
model = Author
集成允许从 SQLAlchemy Column
类型推断Column
类型。
Flask-JsonTools包为您的模型实现了JsonSerializableBase基类。
用法:
from sqlalchemy.ext.declarative import declarative_base
from flask.ext.jsontools import JsonSerializableBase
Base = declarative_base(cls=(JsonSerializableBase,))
class User(Base):
#...
现在User
模型可以神奇地序列化。
如果您的框架不是 Flask,您可以直接抓取代码
出于安全原因,您永远不应返回模型的所有字段。 我更喜欢有选择地选择它们。
Flask 的 json 编码现在支持 UUID、日期时间和关系(并为 flask_sqlalchemy db.Model
类添加了query
和query_class
)。 我已更新编码器如下:
应用程序/json_encoder.py
from sqlalchemy.ext.declarative import DeclarativeMeta
from flask import json
class AlchemyEncoder(json.JSONEncoder):
def default(self, o):
if isinstance(o.__class__, DeclarativeMeta):
data = {}
fields = o.__json__() if hasattr(o, '__json__') else dir(o)
for field in [f for f in fields if not f.startswith('_') and f not in ['metadata', 'query', 'query_class']]:
value = o.__getattribute__(field)
try:
json.dumps(value)
data[field] = value
except TypeError:
data[field] = None
return data
return json.JSONEncoder.default(self, o)
app/__init__.py
# json encoding
from app.json_encoder import AlchemyEncoder
app.json_encoder = AlchemyEncoder
有了这个,我可以选择添加一个__json__
属性,该属性返回我希望编码的字段列表:
app/models.py
class Queue(db.Model):
id = db.Column(db.Integer, primary_key=True)
song_id = db.Column(db.Integer, db.ForeignKey('song.id'), unique=True, nullable=False)
song = db.relationship('Song', lazy='joined')
type = db.Column(db.String(20), server_default=u'audio/mpeg')
src = db.Column(db.String(255), nullable=False)
created_at = db.Column(db.DateTime, server_default=db.func.now())
updated_at = db.Column(db.DateTime, server_default=db.func.now(), onupdate=db.func.now())
def __init__(self, song):
self.song = song
self.src = song.full_path
def __json__(self):
return ['song', 'src', 'type', 'created_at']
我将@jsonapi 添加到我的视图中,返回结果列表,然后我的输出如下:
[
{
"created_at": "Thu, 23 Jul 2015 11:36:53 GMT",
"song":
{
"full_path": "/static/music/Audioslave/Audioslave [2002]/1 Cochise.mp3",
"id": 2,
"path_name": "Audioslave/Audioslave [2002]/1 Cochise.mp3"
},
"src": "/static/music/Audioslave/Audioslave [2002]/1 Cochise.mp3",
"type": "audio/mpeg"
}
]
您可以像这样使用 SqlAlchemy 的自省:
mysql = SQLAlchemy()
from sqlalchemy import inspect
class Contacts(mysql.Model):
__tablename__ = 'CONTACTS'
id = mysql.Column(mysql.Integer, primary_key=True)
first_name = mysql.Column(mysql.String(128), nullable=False)
last_name = mysql.Column(mysql.String(128), nullable=False)
phone = mysql.Column(mysql.String(128), nullable=False)
email = mysql.Column(mysql.String(128), nullable=False)
street = mysql.Column(mysql.String(128), nullable=False)
zip_code = mysql.Column(mysql.String(128), nullable=False)
city = mysql.Column(mysql.String(128), nullable=False)
def toDict(self):
return { c.key: getattr(self, c.key) for c in inspect(self).mapper.column_attrs }
@app.route('/contacts',methods=['GET'])
def getContacts():
contacts = Contacts.query.all()
contactsArr = []
for contact in contacts:
contactsArr.append(contact.toDict())
return jsonify(contactsArr)
@app.route('/contacts/<int:id>',methods=['GET'])
def getContact(id):
contact = Contacts.query.get(id)
return jsonify(contact.toDict())
从这里的答案中获得启发: 将 sqlalchemy 行对象转换为 python dict
更详细的解释。 在您的模型中,添加:
def as_dict(self):
return {c.name: str(getattr(self, c.name)) for c in self.__table__.columns}
str()
用于 python 3,所以如果使用 python 2 使用unicode()
。 它应该有助于反序列化日期。 如果不处理这些,您可以将其删除。
您现在可以像这样查询数据库
some_result = User.query.filter_by(id=current_user.id).first().as_dict()
需要First()
以避免奇怪的错误。 as_dict()
现在将反序列化结果。 反序列化后就可以转成json了
jsonify(some_result)
虽然最初的问题可以追溯到一段时间以前,但这里的答案数量(以及我自己的经验)表明这是一个不平凡的问题,有许多不同的方法,具有不同的复杂性和不同的权衡。
这就是我构建SQLAthanor库的原因,该库扩展了 SQLAlchemy 的声明性 ORM,并具有您可能想要查看的可配置序列化/反序列化支持。
该库支持:
dict
序列化/反序列化password
值,但从不包括出站password
)您可以在此处查看(我希望!)全面的文档: https : //sqlathanor.readthedocs.io/en/latest
希望这可以帮助!
自定义序列化和反序列化。
“from_json” (类方法)基于json数据构建一个Model对象。
“反序列化”只能在实例上调用,并将 json 中的所有数据合并到模型实例中。
“序列化” - 递归序列化
需要__write_only__属性来定义只写属性(例如“password_hash”)。
class Serializable(object):
__exclude__ = ('id',)
__include__ = ()
__write_only__ = ()
@classmethod
def from_json(cls, json, selfObj=None):
if selfObj is None:
self = cls()
else:
self = selfObj
exclude = (cls.__exclude__ or ()) + Serializable.__exclude__
include = cls.__include__ or ()
if json:
for prop, value in json.iteritems():
# ignore all non user data, e.g. only
if (not (prop in exclude) | (prop in include)) and isinstance(
getattr(cls, prop, None), QueryableAttribute):
setattr(self, prop, value)
return self
def deserialize(self, json):
if not json:
return None
return self.__class__.from_json(json, selfObj=self)
@classmethod
def serialize_list(cls, object_list=[]):
output = []
for li in object_list:
if isinstance(li, Serializable):
output.append(li.serialize())
else:
output.append(li)
return output
def serialize(self, **kwargs):
# init write only props
if len(getattr(self.__class__, '__write_only__', ())) == 0:
self.__class__.__write_only__ = ()
dictionary = {}
expand = kwargs.get('expand', ()) or ()
prop = 'props'
if expand:
# expand all the fields
for key in expand:
getattr(self, key)
iterable = self.__dict__.items()
is_custom_property_set = False
# include only properties passed as parameter
if (prop in kwargs) and (kwargs.get(prop, None) is not None):
is_custom_property_set = True
iterable = kwargs.get(prop, None)
# loop trough all accessible properties
for key in iterable:
accessor = key
if isinstance(key, tuple):
accessor = key[0]
if not (accessor in self.__class__.__write_only__) and not accessor.startswith('_'):
# force select from db to be able get relationships
if is_custom_property_set:
getattr(self, accessor, None)
if isinstance(self.__dict__.get(accessor), list):
dictionary[accessor] = self.__class__.serialize_list(object_list=self.__dict__.get(accessor))
# check if those properties are read only
elif isinstance(self.__dict__.get(accessor), Serializable):
dictionary[accessor] = self.__dict__.get(accessor).serialize()
else:
dictionary[accessor] = self.__dict__.get(accessor)
return dictionary
使用 SQLAlchemy 中的内置序列化程序:
from sqlalchemy.ext.serializer import loads, dumps
obj = MyAlchemyObject()
# serialize object
serialized_obj = dumps(obj)
# deserialize object
obj = loads(serialized_obj)
如果您要在会话之间传输对象,请记住使用session.expunge(obj)
将对象与当前会话分离。 要再次附加它,只需执行session.add(obj)
。
这是一个解决方案,可让您根据需要选择要包含在输出中的关系。 注意:这是一个完整的重写,将 dict/str 作为 arg 而不是列表。 修复一些东西..
def deep_dict(self, relations={}):
"""Output a dict of an SA object recursing as deep as you want.
Takes one argument, relations which is a dictionary of relations we'd
like to pull out. The relations dict items can be a single relation
name or deeper relation names connected by sub dicts
Example:
Say we have a Person object with a family relationship
person.deep_dict(relations={'family':None})
Say the family object has homes as a relation then we can do
person.deep_dict(relations={'family':{'homes':None}})
OR
person.deep_dict(relations={'family':'homes'})
Say homes has a relation like rooms you can do
person.deep_dict(relations={'family':{'homes':'rooms'}})
and so on...
"""
mydict = dict((c, str(a)) for c, a in
self.__dict__.items() if c != '_sa_instance_state')
if not relations:
# just return ourselves
return mydict
# otherwise we need to go deeper
if not isinstance(relations, dict) and not isinstance(relations, str):
raise Exception("relations should be a dict, it is of type {}".format(type(relations)))
# got here so check and handle if we were passed a dict
if isinstance(relations, dict):
# we were passed deeper info
for left, right in relations.items():
myrel = getattr(self, left)
if isinstance(myrel, list):
mydict[left] = [rel.deep_dict(relations=right) for rel in myrel]
else:
mydict[left] = myrel.deep_dict(relations=right)
# if we get here check and handle if we were passed a string
elif isinstance(relations, str):
# passed a single item
myrel = getattr(self, relations)
left = relations
if isinstance(myrel, list):
mydict[left] = [rel.deep_dict(relations=None)
for rel in myrel]
else:
mydict[left] = myrel.deep_dict(relations=None)
return mydict
所以举个例子,使用 person/family/homes/rooms ... 把它变成 json 你只需要
json.dumps(person.deep_dict(relations={'family':{'homes':'rooms'}}))
它不是那么简单。 我写了一些代码来做到这一点。 我仍在研究它,它使用 MochiKit 框架。 它基本上使用代理和注册的 JSON 转换器在 Python 和 Javascript 之间转换复合对象。
数据库对象的浏览器端是db.js它需要在基本的Python代理源的proxy.js 。
在 Python 端有基本代理模块。 最后是webserver.py 中的 SqlAlchemy 对象编码器。 它还取决于在models.py文件中找到的元数据提取器。
step1:
class CNAME:
...
def as_dict(self):
return {item.name: getattr(self, item.name) for item in self.__table__.columns}
step2:
list = []
for data in session.query(CNAME).all():
list.append(data.as_dict())
step3:
return jsonify(list)
def alc2json(row):
return dict([(col, str(getattr(row,col))) for col in row.__table__.columns.keys()])
我想我会用这个玩一些代码高尔夫。
仅供参考:我正在使用automap_base,因为我们有一个根据业务需求单独设计的架构。 我今天刚开始使用 SQLAlchemy,但文档指出 automap_base 是 declarative_base 的扩展,这似乎是 SQLAlchemy ORM 中的典型范例,所以我相信这应该可行。
根据Tjorriemorrie的解决方案,它并不喜欢遵循外键,但它只是将列与值匹配并通过 str() 处理列值来处理 Python 类型。 我们的值包括 Python datetime.time 和 decimal.Decimal 类类型结果,因此它可以完成工作。
希望这对任何路过的人有所帮助!
我知道这是一个相当老的帖子。 我采用了@SashaB 给出的解决方案,并根据我的需要进行了修改。
我添加了以下内容:
我的代码如下:
def alchemy_json_encoder(revisit_self = False, fields_to_expand = [], fields_to_ignore = [], fields_to_replace = {}):
"""
Serialize SQLAlchemy result into JSon
:param revisit_self: True / False
:param fields_to_expand: Fields which are to be expanded for including their children and all
:param fields_to_ignore: Fields to be ignored while encoding
:param fields_to_replace: Field keys to be replaced by values assigned in dictionary
:return: Json serialized SQLAlchemy object
"""
_visited_objs = []
class AlchemyEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# don't re-visit self
if revisit_self:
if obj in _visited_objs:
return None
_visited_objs.append(obj)
# go through each field in this SQLalchemy class
fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata' and x not in fields_to_ignore]:
val = obj.__getattribute__(field)
# is this field method defination, or an SQLalchemy object
if not hasattr(val, "__call__") and not isinstance(val, BaseQuery):
field_name = fields_to_replace[field] if field in fields_to_replace else field
# is this field another SQLalchemy object, or a list of SQLalchemy objects?
if isinstance(val.__class__, DeclarativeMeta) or \
(isinstance(val, list) and len(val) > 0 and isinstance(val[0].__class__, DeclarativeMeta)):
# unless we're expanding this field, stop here
if field not in fields_to_expand:
# not expanding this field: set it to None and continue
fields[field_name] = None
continue
fields[field_name] = val
# a json-encodable dict
return fields
return json.JSONEncoder.default(self, obj)
return AlchemyEncoder
希望它可以帮助某人!
在 Flask 下,这可以工作并处理数据时间字段,转换类型的字段
'time': datetime.datetime(2018, 3, 22, 15, 40)
进入
"time": "2018-03-22 15:40:00"
:
obj = {c.name: str(getattr(self, c.name)) for c in self.__table__.columns}
# This to get the JSON body
return json.dumps(obj)
# Or this to get a response object
return jsonify(obj)
以下代码将 sqlalchemy 结果序列化为 json。
import json
from collections import OrderedDict
def asdict(self):
result = OrderedDict()
for key in self.__mapper__.c.keys():
if getattr(self, key) is not None:
result[key] = str(getattr(self, key))
else:
result[key] = getattr(self, key)
return result
def to_array(all_vendors):
v = [ ven.asdict() for ven in all_vendors ]
return json.dumps(v)
叫乐趣,
def all_products():
all_products = Products.query.all()
return to_array(all_products)
AlchemyEncoder 很棒,但有时会因 Decimal 值而失败。 这是一个解决十进制问题的改进编码器 -
class AlchemyEncoder(json.JSONEncoder):
# To serialize SQLalchemy objects
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
model_fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
data = obj.__getattribute__(field)
print data
try:
json.dumps(data) # this will fail on non-encodable values, like other classes
model_fields[field] = data
except TypeError:
model_fields[field] = None
return model_fields
if isinstance(obj, Decimal):
return float(obj)
return json.JSONEncoder.default(self, obj)
当使用 sqlalchemy 连接到数据库时,这是一个高度可配置的简单解决方案。 使用熊猫。
import pandas as pd
import sqlalchemy
#sqlalchemy engine configuration
engine = sqlalchemy.create_engine....
def my_function():
#read in from sql directly into a pandas dataframe
#check the pandas documentation for additional config options
sql_DF = pd.read_sql_table("table_name", con=engine)
# "orient" is optional here but allows you to specify the json formatting you require
sql_json = sql_DF.to_json(orient="index")
return sql_json
虽然是旧帖,可能我没有回答上面的问题,但我想谈谈我的连载,至少它对我有用。
我使用 FastAPI、SqlAlchemy 和 MySQL,但我不使用 orm 模型;
# from sqlalchemy import create_engine
# from sqlalchemy.orm import sessionmaker
# engine = create_engine(config.SQLALCHEMY_DATABASE_URL, pool_pre_ping=True)
# SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
序列化代码
import decimal
import datetime
def alchemy_encoder(obj):
"""JSON encoder function for SQLAlchemy special classes."""
if isinstance(obj, datetime.date):
return obj.strftime("%Y-%m-%d %H:%M:%S")
elif isinstance(obj, decimal.Decimal):
return float(obj)
import json
from sqlalchemy import text
# db is SessionLocal() object
app_sql = 'SELECT * FROM app_info ORDER BY app_id LIMIT :page,:page_size'
# The next two are the parameters passed in
page = 1
page_size = 10
# execute sql and return a <class 'sqlalchemy.engine.result.ResultProxy'> object
app_list = db.execute(text(app_sql), {'page': page, 'page_size': page_size})
# serialize
res = json.loads(json.dumps([dict(r) for r in app_list], default=alchemy_encoder))
如果它不起作用,请忽略我的回答。 我参考这里
https://codeandlife.com/2014/12/07/sqlalchemy-results-to-json-the-easy-way/
通过pip install simplejson
并创建一个类
class Serialise(object):
def _asdict(self):
"""
Serialization logic for converting entities using flask's jsonify
:return: An ordered dictionary
:rtype: :class:`collections.OrderedDict`
"""
result = OrderedDict()
# Get the columns
for key in self.__mapper__.c.keys():
if isinstance(getattr(self, key), datetime):
result["x"] = getattr(self, key).timestamp() * 1000
result["timestamp"] = result["x"]
else:
result[key] = getattr(self, key)
return result
并将这个类继承到每个 orm 类,以便这个_asdict
函数注册到每个 ORM 类和繁荣。 并在任何地方使用 jsonify
(对Sasha B非常出色的答案的微小调整)
这专门将 datetime 对象转换为字符串,在原始答案中将转换为None
:
# Standard library imports
from datetime import datetime
import json
# 3rd party imports
from sqlalchemy.ext.declarative import DeclarativeMeta
class JsonEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
dict = {}
# Remove invalid fields and just get the column attributes
columns = [x for x in dir(obj) if not x.startswith("_") and x != "metadata"]
for column in columns:
value = obj.__getattribute__(column)
try:
json.dumps(value)
dict[column] = value
except TypeError:
if isinstance(value, datetime):
dict[column] = value.__str__()
else:
dict[column] = None
return dict
return json.JSONEncoder.default(self, obj)
class SqlToDict:
def __init__(self, data) -> None:
self.data = data
def to_timestamp(self, date):
if isinstance(date, datetime):
return int(datetime.timestamp(date))
else:
return date
def to_dict(self) -> List:
arr = []
for i in self.data:
keys = [*i.keys()]
values = [*i]
values = [self.to_timestamp(d) for d in values]
arr.append(dict(zip(keys, values)))
return arr
例如:
SqlToDict(data).to_dict()
带有 utf-8 的内置串行器扼流圈无法解码某些输入的无效起始字节。 相反,我选择了:
def row_to_dict(row):
temp = row.__dict__
temp.pop('_sa_instance_state', None)
return temp
def rows_to_list(rows):
ret_rows = []
for row in rows:
ret_rows.append(row_to_dict(row))
return ret_rows
@website_blueprint.route('/api/v1/some/endpoint', methods=['GET'])
def some_api():
'''
/some_endpoint
'''
rows = rows_to_list(SomeModel.query.all())
response = app.response_class(
response=jsonplus.dumps(rows),
status=200,
mimetype='application/json'
)
return response
也许你可以使用这样的类
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy import Table
class Custom:
"""Some custom logic here!"""
__table__: Table # def for mypy
@declared_attr
def __tablename__(cls): # pylint: disable=no-self-argument
return cls.__name__ # pylint: disable= no-member
def to_dict(self) -> Dict[str, Any]:
"""Serializes only column data."""
return {c.name: getattr(self, c.name) for c in self.__table__.columns}
Base = declarative_base(cls=Custom)
class MyOwnTable(Base):
#COLUMNS!
所有对象都有to_dict
方法
在使用一些原始 sql 和未定义的对象时,使用cursor.description
似乎得到了我想要的:
with connection.cursor() as cur:
print(query)
cur.execute(query)
for item in cur.fetchall():
row = {column.name: item[i] for i, column in enumerate(cur.description)}
print(row)
这是一个JSONEncoder
版本,它保留模型列顺序并且只保留递归定义的列和关系字段。 它还格式化大多数 JSON 不可序列化类型:
import json
from datetime import datetime
from decimal import Decimal
import arrow
from sqlalchemy.ext.declarative import DeclarativeMeta
class SQLAlchemyJSONEncoder(json.JSONEncoder):
"""
SQLAlchemy ORM JSON Encoder
If you have a "backref" relationship defined in your SQLAlchemy model,
this encoder raises a ValueError to stop an infinite loop.
"""
def default(self, obj):
if isinstance(obj, datetime):
return arrow.get(obj).isoformat()
elif isinstance(obj, Decimal):
return float(obj)
elif isinstance(obj, set):
return sorted(obj)
elif isinstance(obj.__class__, DeclarativeMeta):
for attribute, relationship in obj.__mapper__.relationships.items():
if isinstance(relationship.__getattribute__("backref"), tuple):
raise ValueError(
f'{obj.__class__} object has a "backref" relationship '
"that would cause an infinite loop!"
)
dictionary = {}
column_names = [column.name for column in obj.__table__.columns]
for key in column_names:
value = obj.__getattribute__(key)
if isinstance(value, datetime):
value = arrow.get(value).isoformat()
elif isinstance(value, Decimal):
value = float(value)
elif isinstance(value, set):
value = sorted(value)
dictionary[key] = value
for key in [
attribute
for attribute in dir(obj)
if not attribute.startswith("_")
and attribute != "metadata"
and attribute not in column_names
]:
value = obj.__getattribute__(key)
dictionary[key] = value
return dictionary
return super().default(obj)
我成功地使用了这个包: https : //github.com/n0nSmoker/SQLAlchemy-serializer
您可以在模型上执行此操作:
from sqlalchemy_serializer import SerializerMixin
class SomeModel(db.Model, SerializerMixin):
...
它添加了完全递归的 to_dict:
item = SomeModel.query.filter(...).one()
result = item.to_dict()
它可以让你制定规则来避免无限递归:
result = item.to_dict(rules=('-somefield', '-some_relation.nested_one.another_nested_one'))
如果您正在使用 Flask 并且只想快速查询:
def get_cats():
sql = text("select * from cat")
sql_params = {}
result = db.session.execute(sql, sql_params)
row_list = result.fetchall()
data = [dict(r) for r in row_list]
response = jsonify({
'data': [{
'categorias': data
}]
})
return response
https://flask-restplus.readthedocs.io/en/stable/marshalling.html
from flask_restplus import fields, Namespace, marshal
api = Namespace("Student data")
db_data = Student_details.query.all()
data_marshal_obj = api.model(" Data", {
"id": fields.String(),
"number": fields.Integer(),
"house_name": fields.String(),
})
data_in_json_serialize = marshal(db_data, data_marshal_obj)}
print(type(data_in_json_serialize )) # <class 'dict'>
经过一番尝试,我想出了自己的解决方案,如下所示
def to_dict(self):
keys = self.__mapper__.attrs.keys()
attrs = vars(self)
return { k : attrs[k] for k in keys}
将as_dict
方法添加到任何 model 的动态方法
from sqlalchemy.inspection import inspect
def implement_as_dict(model):
if not hasattr(model,"as_dict"):
column_names=[]
imodel = inspect(model)
for c in imodel.columns:
column_names.append(c.key)
#define model.as_dict()
def as_dict(self):
d = {}
for c in column_names:
d[c] = getattr(self,c)
return d
setattr(model,"as_dict",as_dict)
#model definition
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
# adding as_dict definition to model
implement_as_dict(User)
那么你可以使用
user = session.query(User).filter_by(name='rick').first()
user.as_dict()
#sample output
{"id":1,"name":"rick"}
我的实现
def obj_to_dict(obj, remove=['_sa_instance_state'], debug=False):
result = {}
if type(obj).__name__ == "Row":
return dict(obj)
obj = obj.__dict__
for key in obj:
if key in remove:
continue
result[key] = obj[key]
if debug:
print(result)
return result
我使用(太多?)字典:
def serialize(_query):
#d = dictionary written to per row
#D = dictionary d is written to each time, then reset
#Master = dictionary of dictionaries; the id Key (int, unique from database)
from D is used as the Key for the dictionary D entry in Master
Master = {}
D = {}
x = 0
for u in _query:
d = u.__dict__
D = {}
for n in d.keys():
if n != '_sa_instance_state':
D[n] = d[n]
x = d['id']
Master[x] = D
return Master
使用flask(包括jsonify)和flask_sqlalchemy 运行以将输出打印为JSON。
使用 jsonify(serialize()) 调用函数。
适用于我迄今为止尝试过的所有 SQLAlchemy 查询(运行 SQLite3)
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