Python 如何使用SQLAlchemy仅创建一个表？_Python_Mysql_Python 3.x_Sqlalchemy

Python 如何使用SQLAlchemy仅创建一个表？

python mysql python-3.x sqlalchemy

Python 如何使用SQLAlchemy仅创建一个表？,python,mysql,python-3.x,sqlalchemy,Python,Mysql,Python 3.x,Sqlalchemy,我无法使用SQLAlchemy创建单个表我可以通过调用Base.metadata.create\u all（engine）来创建它，但是随着表的数量增加，这个调用需要很长时间我动态创建表类，然后填充它们 from sqlalchemy import create_engine, Column, Integer, Sequence, String, Date, Float, BIGINT from sqlalchemy.ext.declarative import declarative_ba

我无法使用SQLAlchemy创建单个表

我可以通过调用

Base.metadata.create\u all（engine）

来创建它，但是随着表的数量增加，这个调用需要很长时间

我动态创建表类，然后填充它们

from sqlalchemy import create_engine, Column, Integer, Sequence, String, Date, Float, BIGINT
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class HistoricDay():

    id = Column(Integer, Sequence('id_seq'), primary_key=True)
    #  Date, Open, High, Low, Close, Volume, Adj Close
    date = Column(Date)
    open = Column(Float)
    high = Column(Float)
    low = Column(Float)
    close = Column(Float)
    volume = Column(BIGINT)
    adjClose = Column(Float)

    def __init__(self, date, open, high, low, close, volume, adjClose):
        self.date = date
        self.open = open
        self.high = high
        self.low = low
        self.close = close
        self.volume = volume
        self.adjClose = adjClose

def build_daily_history_table_repr(self):
        return "<"+self.__tablename__+"('{}','{}','{}','{}','{}','{}','{}','{}')>".format(self.id, self.date, self.open, self.high, self.low, self.close, self.volume, self.adjClose)

def build_daily_history_table(ticket):
    classname = ticket+"_HistoricDay"
    globals()[classname] = type(classname, (HistoricDay,Base), {'__tablename__' : ticket+"_daily_history"})
    setattr(globals()[classname], '__repr__', build_daily_history_table_repr)

# Initialize the database :: Connection & Metadata retrieval
engine = create_engine('mysql+cymysql://root@localhost/gwc?charset=utf8&use_unicode=0', pool_recycle=3600) # ,echo = True

# SqlAlchemy :: Session setup
Session = sessionmaker(bind=engine)

# Create all tables that do not already exist
Base.metadata.create_all(engine)

# SqlAlchemy :: Starts a session
session = Session()

ticketList = getTicketList()

for ticket in ticketList:
    build_daily_history_table(ticket)
    class_name = ticket+"_HistoricDay"

    meta_create_all_timer = time.time()
    # Create all tables that do not already exist
    # globals()[class_name]('2005-07-24',0,0,0,0,0,0).create(engine)  #doesn't work
    #(globals()[class_name]).__table__.create(engine) #doesn't work
    # session.commit() #doesn't work

    #Base.metadata.create_all(engine) # works but gets very slow
    print("  meta_create_all_timer {}s".format(time.time()-meta_create_all_timer))

    data = getData(ticket)

    for m_date, m_open, m_close, m_high, m_low, m_volume, m_adjClose in data:
        entry = globals()[class_name](m_date, m_open, m_high, m_low, m_close, m_volume, m_adjClose)
        session.add(entry)

    session.commit()

但是，我无法理解如何使用

declarative_base（）

执行与

Table

相同的操作

对于从

声明性_base（）

继承的类，如何做到这一点

上面，声明性的_base（）callable从所有映射类都应该继承的。当类定义为完成后，将生成一个新表和映射器（）

生成的表格和映射器可通过

\uuuuu table\uuuu

和

映射器属性
（来自）
因此：
def build_daily_history_table(ticket):
    classname = ticket + "_HistoricDay"
    ticket = type(classname, (Base, HistoricDay), {'__tablename__' : ticket+"_daily_history"})
    ticket.__repr__ =  build_daily_history_table_repr
    return ticket

build_daily_history_table("test").__table__.create(bind = engine)

2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE test_daily_history (
    id INTEGER NOT NULL, 
    date DATE, 
    open FLOAT, 
    high FLOAT, 
    low FLOAT, 
    close FLOAT, 
    volume BIGINT, 
    "adjClose" FLOAT, 
    PRIMARY KEY (id)
)


2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine ()
2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine COMMIT

输出：
def build_daily_history_table(ticket):
    classname = ticket + "_HistoricDay"
    ticket = type(classname, (Base, HistoricDay), {'__tablename__' : ticket+"_daily_history"})
    ticket.__repr__ =  build_daily_history_table_repr
    return ticket

build_daily_history_table("test").__table__.create(bind = engine)

2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE test_daily_history (
    id INTEGER NOT NULL, 
    date DATE, 
    open FLOAT, 
    high FLOAT, 
    low FLOAT, 
    close FLOAT, 
    volume BIGINT, 
    "adjClose" FLOAT, 
    PRIMARY KEY (id)
)


2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine ()
2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine COMMIT

这要归功于评论/更正，或者我可能会提出类似于以下内容的建议：
Base.metadata.tables["ticket_daily_history"].create(bind = engine)

建议：
def build_daily_history_table(ticket):
    classname = ticket + "_HistoricDay"
    ticket = type(classname, (Base, HistoricDay), {'__tablename__' : ticket+"_daily_history"})
    ticket.__repr__ =  build_daily_history_table_repr
    return ticket

build_daily_history_table("test").__table__.create(bind = engine)

2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE test_daily_history (
    id INTEGER NOT NULL, 
    date DATE, 
    open FLOAT, 
    high FLOAT, 
    low FLOAT, 
    close FLOAT, 
    volume BIGINT, 
    "adjClose" FLOAT, 
    PRIMARY KEY (id)
)


2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine ()
2013-10-04 22:36:53,263 INFO sqlalchemy.engine.base.Engine COMMIT

在build\u daily\u history\u table
中使用的方法可能是最不优雅的方法之一，主要原因是它污染了/弄乱了数据库。要创建特定的表，给tables
参数以create\u all（）
方法就足够了
Base.metadata.create_all(engine, tables=table_objects)

表_对象等于：
table_objects = [HistoricDay.__table__]

或
我给你看了一张桌子。您可以根据需要增加表的数量
参考：
用一行创建所有不存在的表。默认情况下，首先检查表是否存在
Base.metadata.create_all(db_engine, Base.metadata.tables.values(),checkfirst=True)

使用表名称创建一个目标表

Base.metadata.create_all(db_engine, Base.metadata.tables[table_name],checkfirst=True)

它与声明性\u base
完美配合
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()
TABLE_PREFIX = "decision_"


class Stock(Base):
    __tablename__ = '{}stocks'.format(TABLE_PREFIX)

    id = Column(Integer, primary_key=True)
    name = Column(String)

class StagePerformance(Base):
    __tablename__ = '{}stage_performance'.format(TABLE_PREFIX)

    id = Column(Integer, primary_key=True)
    date = Column(DateTime)
    stock = relationship("Stock", back_populates="stage_performances")
    period = Column(Integer )
    open = Column(Float)
    high = Column(Float)
    low = Column(Float)
    close = Column(Float)
    change_ratio = Column(Float)
    turnover = Column(Float)
    volume = Column(Float)

它应该是HistoricDay（Base）
No，因为HistoricDay没有属性tablename。生成的类继承自Base:globals（）[classname]=type（classname，（HistoricDay，Base），{'tablename'：ticket+“\u daily\u history”}）我尝试过，但回溯（最近一次调用）：m_init（）文件“autoPopulate.py”第493行，m_init（）文件“autoPopulate.py”，第422行，m_init state=success\u state（ticket）文件“autoPopulate.py”，第306行，在success\u state globals（）[class\u name].create（engine）AttributeError:type对象'HMN\u HistoricDay'没有属性'create'
HistoricDay.\uu table\uuuuuuuuuuu.create（engine）
对于cymysql连接器，我必须使用\uu table\uuuuuuuu.create（engine，checkfirst=True）
据我所见，@javex的评论正是我们大多数人在这里寻找的，因此在问题中再强调一点可能会有用。第二个选项对我有用：Base.metadata.create_all（engine，tables=[Product._table_u]）。谢谢