Python-SQLAlchemy中,定义表对象时,何时应该写__init__,何时不写?

Question

描述问题

代码见: http://docs.sqlalchemy.org/en...

从Base继承的表对象, 何时写__init__? (标准是啥?)

我自己的观点是: 貌似写__init__完全没有必要

上下文环境

Python3
SQLAlchemy

Metadata-Version: 1.1
Name: SQLAlchemy
Version: 1.0.11
Summary: Database Abstraction Library
Home-page: http://www.sqlalchemy.org
Author: Mike Bayer

重现

相关代码

"""model.py

The datamodel, which represents Person that has multiple
Address objects, each with PostalCode, City, Country.

Person --(1..n)--> Address
Address --(has a)--> PostalCode
PostalCode --(has a)--> City
City --(has a)--> Country

"""
from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship
from .caching_query import FromCache, RelationshipCache
from .environment import Base, bootstrap

class Country(Base):
    __tablename__ = 'country'

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

    def __init__(self, name):
        self.name = name

class City(Base):
    __tablename__ = 'city'

    id = Column(Integer, primary_key=True)
    name = Column(String(100), nullable=False)
    country_id = Column(Integer, ForeignKey('country.id'), nullable=False)
    country = relationship(Country)

    def __init__(self, name, country):
        self.name = name
        self.country = country

class PostalCode(Base):
    __tablename__ = 'postal_code'

    id = Column(Integer, primary_key=True)
    code = Column(String(10), nullable=False)
    city_id = Column(Integer, ForeignKey('city.id'), nullable=False)
    city = relationship(City)

    @property
    def country(self):
        return self.city.country

    def __init__(self, code, city):
        self.code = code
        self.city = city

class Address(Base):
    __tablename__ = 'address'

    id = Column(Integer, primary_key=True)
    person_id = Column(Integer, ForeignKey('person.id'), nullable=False)
    street = Column(String(200), nullable=False)
    postal_code_id = Column(Integer, ForeignKey('postal_code.id'))
    postal_code = relationship(PostalCode)

    @property
    def city(self):
        return self.postal_code.city

    @property
    def country(self):
        return self.postal_code.country

    def __str__(self):
        return "%s\t"\
              "%s, %s\t"\
              "%s" % (self.street, self.city.name,
                self.postal_code.code, self.country.name)

class Person(Base):
    __tablename__ = 'person'

    id = Column(Integer, primary_key=True)
    name = Column(String(100), nullable=False)
    addresses = relationship(Address, collection_class=set)

    def __init__(self, name, *addresses):
        self.name = name
        self.addresses = set(addresses)

    def __str__(self):
        return self.name

    def __repr__(self):
        return "Person(name=%r)" % self.name

    def format_full(self):
        return "\t".join([str(x) for x in [self] + list(self.addresses)])

# Caching options.   A set of three RelationshipCache options
# which can be applied to Query(), causing the "lazy load"
# of these attributes to be loaded from cache.
cache_address_bits = RelationshipCache(PostalCode.city, "default").\
                and_(
                    RelationshipCache(City.country, "default")
                ).and_(
                    RelationshipCache(Address.postal_code, "default")
                )

bootstrap()

报错信息

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已经尝试哪些方法仍然没有解决(附上相关链接)

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