[英]Update SQLAlchemy orm object with changed python dict
在實施可變字典時會遇到問題,該字典將對內容的更改做出反應。 我已經成功設置SQLAlchemy來管理添加和刪除。 但是,對存儲的dict的內容所做的更改不會“觸發” SQLAlchemy數據庫的更新。
我在stackoverflow上發現了其他一些建議:
默認情況下,SQLAlchemy不跟蹤dict屬性內部的更改。 要使其跟蹤更改,可以使用可變擴展名:
我在這里按照示例操作, 如何實現可變的PickleTypes,它們在更改時會自動更新
但是,我無法使其正常工作。 在我的示例中,當我從Column(PickleType)更改為Column(MutableDict.as_mutable(PickleType))時,SQLAlchemy會話不再找到該對象。 下面的代碼說明了我正在嘗試做的事情。
第一個代碼是我設置數據庫的地方,第二個代碼是我試圖向某人添加事務的地方。 我設法添加和刪除交易,但不更改它們。 因此,為什么我嘗試使用MutableDict類,但是我似乎並不完全理解它。
設置SQL數據庫:(sqlalchemy_declarative.py)
from sqlalchemy import Column, ForeignKey, Integer, String, PickleType
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.mutable import Mutable
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine
Base = declarative_base()
class MutableDict(Mutable, dict):
@classmethod
def coerce(cls, key, value):
if not isinstance(value, MutableDict):
if isinstance(value, dict):
return MutableDict(value)
return Mutable.coerce(key, value)
else:
return value
def __delitem(self, key):
dict.__delitem__(self, key)
self.changed()
def __setitem__(self, key, value):
dict.__setitem__(self, key, value)
self.changed()
def __getstate__(self):
return dict(self)
def __setstate__(self, state):
self.update(self)
class Person(Base):
__tablename__ = 'person_object'
# Here we define columns for the table person
# Notice that each column is also a normal Python instance attribute.
id = Column(Integer, primary_key=True)
first_name = Column(String, nullable=False)
last_name = Column(String, nullable=False)
def __str__(self): # prints when treated as string (for use interface)
return f"Primary id: {self.id} \n" \
f"First name: {self.first_name}"
class Transactions(Base):
__tablename__ = 'transactions'
# Here we define columns for the table address.
# Notice that each column is also a normal Python instance attribute.
id = Column(Integer, primary_key=True)
transactions = Column(MutableDict.as_mutable(PickleType))
# transactions = Column(PickleType)
person_object_id = Column(Integer, ForeignKey('person_object.id'))
person_object = relationship(Person)
def update(self, tmp_dict):
for key, value in tmp_dict.items():
print(key, value)
setattr(self, self.transactions[f'{key}'], value)
def create_db():
# Create an engine that stores data in the local directory's
# sqlalchemy_example.db file.
engine = create_engine('sqlite:///person.db')
# Create all tables in the engine. This is equivalent to "Create Table"
# statements in raw SQL.
Base.metadata.create_all(engine)
示例代碼:
from sqlalchemy_declarative import Person, Base, Transactions
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
import sqlalchemy_declarative as sqlalchemy_declarative
def main():
sqlalchemy_declarative.create_db()
engine = create_engine('sqlite:///person.db')
Base.metadata.bind = engine
db_session = sessionmaker()
db_session.bind = engine
session = db_session()
transaction1 = {'item1': 'banana',
'item2': 'apple',
'item3': 'sugar',
'item4': 'coke',
'item5': 'candy'}
transaction2 = {'item1': 'pizza',
'item2': 'water'}
new_obj = Person(first_name='Bob', last_name='Smith')
session.add(new_obj)
new_transaction = Transactions(transactions=transaction1, person_object=new_obj)
session.add(new_transaction)
new_transaction = Transactions(transactions=transaction2, person_object=new_obj)
session.add(new_transaction)
session.commit()
test = session.query(Transactions).all()
for tmp in test:
print(type(tmp.transactions))
print(tmp.transactions == transaction1)
test2 = session.query(Transactions).filter(Transactions.transactions == transaction1).all()
print(test2)
transaction1 = {'item1': 'banana',
'item2': 'apple',
'item3': 'sugar',
'item4': 'coke',
'item5': 'pineapple'}
test2.update(transaction1)
session.commit()
all_transactions = session.query(Transactions).all()
for tmp in all_transactions:
print(tmp.transactions)
if __name__ == '__main__':
main()
但是,test2篩選器找不到與transaction1字典匹配的任何事務。 我懷疑這與字典存儲為MutableDict而不是Dict的事實有關。 但是,我要怎么做以及添加后如何編輯和更改transaction1。
TLDR:我想更改我的字典中使用SQLAlchemy存儲為ORM的內容。
我意識到,不用使用.filter方法就可以解決我的問題。 因此,以下示例可以正常工作。
transaction1 = {'item1': 'banana',
'item2': 'apple',
'item3': 'sugar',
'item4': 'coke',
'item5': 'candy'}
transaction2 = {'item1': 'pizza',
'item2': 'water'}
new_obj = Person(first_name='Bob', last_name='Smith')
session.add(new_obj)
new_transaction = Transactions(transactions=transaction1, person_object=new_obj)
session.add(new_transaction)
new_transaction = Transactions(transactions=transaction2, person_object=new_obj)
session.add(new_transaction)
session.commit()
test = session.query(Transactions).all()
for tmp in test:
print(tmp.transactions)
new_transaction.transactions['item1'] = 'curry banana'
session.commit()
test = session.query(Transactions).all()
for tmp in test:
print(tmp.transactions)
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