python - 如何使用 SQLAlchemy 声明此列

Question

我有一个 MySQL 表，其中一列是小数。它是使用以下参数创建的:

 `ratio` decimal(5,3) DEFAULT NULL,

到目前为止，我整理的示例脚本非常简单。

import sys 
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String

Session = sessionmaker(bind=engine)
session = Session()
Base = declarative_base()

class DailyProjections(Base):
  __tablename__ = 'daily_projections'

  id = Column(Integer, primary_key=True)
  name = Column(String(100))

如何在此处声明比率列？

Answer 1

来自docs :

The Numeric type is designed to receive data from a database type that is explicitly known to be a decimal type (e.g. DECIMAL, NUMERIC, others) and not a floating point type (e.g. FLOAT, REAL, others).

所以你这样声明:

ratio = Column(Numeric(5, 3), nullable=True)