我无法使用 SQLAlchemy 创建单个表。
我可以通过调用Base.metadata.create_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()
我在 documentation 中看到了你可以做到的
engine = create_engine('sqlite:///:memory:')
meta = MetaData()
employees = Table('employees', meta,
Column('employee_id', Integer, primary_key=True),
Column('employee_name', String(60), nullable=False, key='name'),
Column('employee_dept', Integer, ForeignKey("departments.department_id"))
)
employees.create(engine)
但是,我无法弄清楚如何使用 declarative_base()
执行与 Table
相同的操作。
如何使用继承自 declarative_base()
的类来做到这一点?
最佳答案
Above, the declarative_base() callable returns a new base class from which all mapped classes should inherit. When the class definition is completed, a new Table and mapper() will have been generated.
The resulting table and mapper are accessible via
__table__
and__mapper__
attributes
(来自here)
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)
输出:
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
归功于 javex's评论/更正,或者我可能会提出类似的建议:
Base.metadata.tables["ticket_daily_history"].create(bind = engine)
建议:
build_daily_history_table
中使用的方法可能是最不优雅的做事方式之一,主要是因为它污染/弄乱了 namespace .
关于python - 如何使用 SQLAlchemy 只创建一张表?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19175311/