Re: [sqlalchemy] Re: dynamic classes and tables
On Feb 9, 2011, at 1:52 AM, farcat wrote:
Thank you, that works.
Is there any way to later add or remove attributes, using the
declarative system?
add yes, just plug them on,
http://www.sqlalchemy.org/docs/orm/extensions/declarative.html#defining-attributes,
removal not so much since the mapper has internal state corresponding to each
attribute.Usually object oriented application models don't change
constantly as the application runs.
Cheers, Lars
On Feb 8, 10:46 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Feb 8, 2011, at 3:52 PM, farcat wrote:
Hi everyone,
I am new to sqlalchemy and figuring out whether it is right for my
project. What I am looking for is the ability to change classes and
tables on the flight, with as much freedom as possible, potentially
having metaclasses figuring out the difference between versions and
updating the database accordingly. Additionally I would like to import
databases and automatically generate class definitions. Some code I
tried:
code
from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relation, sessionmaker
Base = declarative_base()
def Init(self, title=None, year=None):
self.title = title
self.year = year
def Repr(self):
return Movie(%r, %r, %r) % (self.title, self.year,
self.director)
Movie = type(Movie, (Base,),{'__tablename__': movies,
id:Column(Integer, primary_key=True),
title: Column(String(255), nullable=False),
year: Column(Integer),
directed_by: Column(Integer,
ForeignKey('directors.id')),
director: relation(Director, backref='movies',
lazy=False)})
setattr(Movie, __init__, classmethod(Init))
setattr(Movie, __repr__, classmethod(Repr))
class Director(Base):
__tablename__ = 'directors'
id = Column(Integer, primary_key=True)
name = Column(String(50), nullable=False, unique=True)
def __init__(self, name=None):
self.name = name
def __repr__(self):
return Director(%r) % (self.name)
engine = create_engine('sqlite:///meta.db', echo=True)
Base.metadata.create_all(engine)
if __name__ == __main__:
Session = sessionmaker(bind=engine)
session = Session()
m1 = Movie(Star Trek, 2009)
m1.director = Director(JJ Abrams)
d2 = Director(George Lucas)
d2.movies = [Movie(Star Wars, 1977), Movie(THX 1138, 1971)]
try:
session.add(m1)
session.add(d2)
session.commit()
except:
session.rollback()
alldata = session.query(Movie).all()
for somedata in alldata:
print somedata
\code
with as error:
2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
PRAGMA table_info(directors)
2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
()
Traceback (most recent call last):
File D:\Documents\Code\NetBeans\test\alchemy\src\alchemy.py, line
49, in module
m1.director = Director(JJ Abrams)
File C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py,
line 158, in __set__
2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
PRAGMA table_info(movies)
2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
()
self.impl.set(instance_state(instance),
AttributeError: 'Movie' object has no attribute '_sa_instance_state'
Can anyone shed some light or explain the error message?
your __init__ monkeypatch is interfering with SQLA's wrapping of this method.
Try
Movie = type(Movie, (Base,),{'__tablename__': movies,
__init__:Init,
id:Column(Integer, primary_key=True),
title: Column(String(255), nullable=False),
year: Column(Integer),
directed_by: Column(Integer,ForeignKey('directors.id')),
director: relation(Director,
backref='movies',lazy=False)})
instead.
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[sqlalchemy] Re: dynamic classes and tables
Thank you, that works.
Is there any way to later add or remove attributes, using the
declarative system?
Cheers, Lars
On Feb 8, 10:46 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Feb 8, 2011, at 3:52 PM, farcat wrote:
Hi everyone,
I am new to sqlalchemy and figuring out whether it is right for my
project. What I am looking for is the ability to change classes and
tables on the flight, with as much freedom as possible, potentially
having metaclasses figuring out the difference between versions and
updating the database accordingly. Additionally I would like to import
databases and automatically generate class definitions. Some code I
tried:
code
from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relation, sessionmaker
Base = declarative_base()
def Init(self, title=None, year=None):
self.title = title
self.year = year
def Repr(self):
return Movie(%r, %r, %r) % (self.title, self.year,
self.director)
Movie = type(Movie, (Base,),{'__tablename__': movies,
id:Column(Integer, primary_key=True),
title: Column(String(255), nullable=False),
year: Column(Integer),
directed_by: Column(Integer,
ForeignKey('directors.id')),
director: relation(Director, backref='movies',
lazy=False)})
setattr(Movie, __init__, classmethod(Init))
setattr(Movie, __repr__, classmethod(Repr))
class Director(Base):
__tablename__ = 'directors'
id = Column(Integer, primary_key=True)
name = Column(String(50), nullable=False, unique=True)
def __init__(self, name=None):
self.name = name
def __repr__(self):
return Director(%r) % (self.name)
engine = create_engine('sqlite:///meta.db', echo=True)
Base.metadata.create_all(engine)
if __name__ == __main__:
Session = sessionmaker(bind=engine)
session = Session()
m1 = Movie(Star Trek, 2009)
m1.director = Director(JJ Abrams)
d2 = Director(George Lucas)
d2.movies = [Movie(Star Wars, 1977), Movie(THX 1138, 1971)]
try:
session.add(m1)
session.add(d2)
session.commit()
except:
session.rollback()
alldata = session.query(Movie).all()
for somedata in alldata:
print somedata
\code
with as error:
2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
PRAGMA table_info(directors)
2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
()
Traceback (most recent call last):
File D:\Documents\Code\NetBeans\test\alchemy\src\alchemy.py, line
49, in module
m1.director = Director(JJ Abrams)
File C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py,
line 158, in __set__
2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
PRAGMA table_info(movies)
2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
()
self.impl.set(instance_state(instance),
AttributeError: 'Movie' object has no attribute '_sa_instance_state'
Can anyone shed some light or explain the error message?
your __init__ monkeypatch is interfering with SQLA's wrapping of this method.
Try
Movie = type(Movie, (Base,),{'__tablename__': movies,
__init__:Init,
id:Column(Integer, primary_key=True),
title: Column(String(255), nullable=False),
year: Column(Integer),
directed_by: Column(Integer,ForeignKey('directors.id')),
director: relation(Director,
backref='movies',lazy=False)})
instead.
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athttp://groups.google.com/group/sqlalchemy?hl=en.
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