问题描述
在为 sql alchemy 定义类时，是否可以避免键入列的名称和数据类型，例如假设您有：
from sqlalchemy import Column, Date, Integer, String, Numeric
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Fruit(Base):
__tablename__ = 'Fruits'
# names and datatypes of columns
date_of_record = Column(Date, primary_key=True)
number_of_apples = Column(Integer)
number_of_pears = Column(Integer)
是否可以使用循环重新创建最后一部分？ 例如，如果您想将列名和类型作为输入：
column_names = ['date_of_record', 'number_of_apples', 'number_of_pears']
column_types = [Date, Integer, Integer]
class Fruit(Base):
__tablename__ = 'Fruits'
def __init__(self, column_names, column_types):
for index, (name, type) in enumerate(zip(column_names, column_types)):
if index == 0:
setattr(self, name, Column(type, primary_key = True))
else:
setattr(self, name, Column(type))
但是，这会引发 ArgumentError：Mapper Mapper|Fruit|Fruits 无法为映射表“Fruits”组装任何主键列
是否有人能够提供一个工作示例，说明在使用 sql alchemy 时如何将列名和类型用作类定义中的变量？
1楼
实际上是的，您可以这样做，但是您需要使用Table()和sqlalchemy.orm.mapper创建您的数据库。
你需要做这样的事情：
from sqlalchemy import create_engine, MetaData, Table, Column
from sqlalchemy import Integer, Date # Insert your types here
from sqlalchemy.orm import mapper
engine = create_engine('sqlite:///fruits.db') # Here you need to insert your own path to db
column_names = ['date_of_record', 'number_of_apples', 'number_of_pears']
column_types = [Date, Integer, Integer]
# Adding columns
columns = list()
for index, (name, type) in enumerate(zip(column_names, column_types)):
if index == 0:
columns.append(Column(name, type, primary_key = True))
else:
columns.append(Column(name, type))
metadata = MetaData()
fruits_table = Table('Fruits', metadata, *columns)
metadata.create_all(engine) # Create table
class Fruit(Base):
# You can make initialization method here
pass
print(mapper(Fruit, fruits_table)) # Create a Mapper and print it
现在，要进行会话，您需要执行以下操作：
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine) # Use an engine with your database
session = Session()
test_fruit = Fruit() # You can initialize it, if you will make __init__ method
test_fruit.number_of_apples = 2
test_fruit.number_of_pears = 3
session.add(test_fruit)
session.commit()
希望我的回答能帮到你！