擅长:python、mysql、java
<p>如果由于某些原因需要显式地创建序列(如设置起始值),并且仍然需要与使用<code>Column(Integer, primary_key=True)</code>符号时相同的默认值行为,则可以使用以下代码完成该操作:</p>
<pre><code>#!/usr/bin/env python
from sqlalchemy import create_engine, Column, Integer, String, Sequence
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
USER_ID_SEQ = Sequence('user_id_seq') # define sequence explicitly
class User(Base):
__tablename__ = 'users'
# use sequence in column definition, and pass .next_value() as server_default
id = Column(Integer, USER_ID_SEQ, primary_key=True, server_default=USER_ID_SEQ.next_value())
name = Column(String(50))
fullname = Column(String(50))
password = Column(String(12))
def __repr__(self):
return "<User(name='%s', fullname='%s', password='%s')>" % (
self.name, self.fullname, self.password)
db_url = 'postgresql://localhost/serial'
engine = create_engine(db_url, echo=True)
Base.metadata.create_all(engine)
</code></pre>