Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
def get_properties(tablename, map):
table_inspector = reflection.Inspector.from_engine(DB_ENGINE.connect())
table = Table(tablename, metadata)
table_inspector.reflecttable(table, None)
columns = []
for child in table.get_children():
if isinstance(child, Column):
column = list(child.base_columns)[0]
column.table = None
columns.append(column)
return dict([(map[column.key], column) for column in columns])
class CustomDeclarativeMeta(DeclarativeMeta):
def __new__(cls, name, bases, attrs):
attrs.update(get_properties(attrs.get('__tablename__'),
attrs.get('__map__')))
return super(CustomDeclarativeMeta, cls).__new__(cls, name, bases,
attrs)
# Base = declarative_base(metaclass=CustomDeclarativeMeta)
Base = declarative_base()
class Enum_SampleBase):
__tablename__ = 'Enum_Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = CustomDeclarativeMeta
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
Unfortunately, this isn't working. I want to declare column types by
getting them from a table that's already created in the database.
On Wed, Jul 3, 2013 at 11:11 AM, Michael Bayer mike...@zzzcomputing.comwrote:
your metaclass must derive from the DeclarativeMeta class.
Also, I disagree that you need this metaclass, what you're trying to do
is very easy using mixins, which are supported in version 0.6:
http://docs.sqlalchemy.org/en/rel_0_6/orm/extensions/declarative.html#mixing-in-columns
On Jul 3, 2013, at 12:44 AM, Ven Karri praveen.venk...@gmail.com wrote:
I use: Python 2.6 and sqlalchemy 0.6.1
This is what I am trying to do:
from sqlalchemy.types import (
Integer,
String,
Boolean
)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class SampleMeta(type):
def __new__(cls, name, bases, attrs):
attrs.update({ 'id': Column('Id', Integer, primary_key=True),
'name': Column('Name', String),
'description': Column('Description', String),
'is_active': Column('IsActive', Boolean)
})
return super(SampleMeta, cls).__new__(cls, name, bases, attrs)
class Sample(Base):
__tablename__ = 'Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = SampleMeta
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
And the error I am getting is this:
TypeError: Error when calling the metaclass bases
metaclass conflict: the metaclass of a derived class must be a
(non-strict) subclass of the metaclasses of all its bases
Now, if I do the same thing above by using
class Sample(object)
instead of
class Sample(Base)
it works absolutely fine.
I need to update the attributes of the class dynamically. So, I will be
using dynamic attribute and column names. And I need the above piece code
to work in order to be able to get there.
**Please help**
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
Sorry, it should've been:
class Enum_Sample(Base):
Typo.
On Mon, Aug 26, 2013 at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
def get_properties(tablename, map):
table_inspector = reflection.Inspector.from_engine(DB_ENGINE.connect())
table = Table(tablename, metadata)
table_inspector.reflecttable(table, None)
columns = []
for child in table.get_children():
if isinstance(child, Column):
column = list(child.base_columns)[0]
column.table = None
columns.append(column)
return dict([(map[column.key], column) for column in columns])
class CustomDeclarativeMeta(DeclarativeMeta):
def __new__(cls, name, bases, attrs):
attrs.update(get_properties(attrs.get('__tablename__'),
attrs.get('__map__')))
return super(CustomDeclarativeMeta, cls).__new__(cls, name, bases,
attrs)
# Base = declarative_base(metaclass=CustomDeclarativeMeta)
Base = declarative_base()
class Enum_SampleBase):
__tablename__ = 'Enum_Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = CustomDeclarativeMeta
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
Unfortunately, this isn't working. I want to declare column types by
getting them from a table that's already created in the database.
On Wed, Jul 3, 2013 at 11:11 AM, Michael Bayer
mike...@zzzcomputing.comwrote:
your metaclass must derive from the DeclarativeMeta class.
Also, I disagree that you need this metaclass, what you're trying to do
is very easy using mixins, which are supported in version 0.6:
http://docs.sqlalchemy.org/en/rel_0_6/orm/extensions/declarative.html#mixing-in-columns
On Jul 3, 2013, at 12:44 AM, Ven Karri praveen.venk...@gmail.com wrote:
I use: Python 2.6 and sqlalchemy 0.6.1
This is what I am trying to do:
from sqlalchemy.types import (
Integer,
String,
Boolean
)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class SampleMeta(type):
def __new__(cls, name, bases, attrs):
attrs.update({ 'id': Column('Id', Integer,
primary_key=True),
'name': Column('Name', String),
'description': Column('Description', String),
'is_active': Column('IsActive', Boolean)
})
return super(SampleMeta, cls).__new__(cls, name, bases, attrs)
class Sample(Base):
__tablename__ = 'Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = SampleMeta
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
And the error I am getting is this:
TypeError: Error when calling the metaclass bases
metaclass conflict: the metaclass of a derived class must be a
(non-strict) subclass of the metaclasses of all its bases
Now, if I do the same thing above by using
class Sample(object)
instead of
class Sample(Base)
it works absolutely fine.
I need to update the attributes of the class dynamically. So, I will be
using dynamic attribute and column names. And I need the above piece code
to work in order to be able to get there.
**Please help**
--
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is more
like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column and add
the .key of your choice, and saves on code by making use of the existing
DeferredReflection mixin instead of hand-coding it. There's many more variants
on this kind of thing as well. DeferredReflection is using some
not-yet-public APIs to do its work, but there are other ways of deferring the
mapping as well (typically by overriding the __mapper__ attribute). Basically
your class creates itself an empty Table object, to which we apply events.
then DeferredReflection.prepare() fills in those Table objects with their
columns using reflection.
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@classmethod
def __declare_last__(cls):
@event.listens_for(cls.__table__, column_reflect)
def new_col(inspector, table, column_info):
column_info['key'] = cls.__map__.get(column_info['name'],
column_info['name'])
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
def get_properties(tablename, map):
table_inspector = reflection.Inspector.from_engine(DB_ENGINE.connect())
table = Table(tablename, metadata)
table_inspector.reflecttable(table, None)
columns = []
for child in table.get_children():
if isinstance(child, Column):
column = list(child.base_columns)[0]
column.table = None
columns.append(column)
return dict([(map[column.key], column) for column in columns])
class CustomDeclarativeMeta(DeclarativeMeta):
def __new__(cls, name, bases, attrs):
attrs.update(get_properties(attrs.get('__tablename__'),
attrs.get('__map__')))
return super(CustomDeclarativeMeta, cls).__new__(cls, name, bases,
attrs)
# Base = declarative_base(metaclass=CustomDeclarativeMeta)
Base = declarative_base()
class Enum_SampleBase):
__tablename__ = 'Enum_Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = CustomDeclarativeMeta
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
Unfortunately, this isn't working. I want to declare column types by getting
them from a table that's already created in the database.
On Wed, Jul 3, 2013 at 11:11 AM, Michael Bayer mike...@zzzcomputing.com
wrote:
your metaclass must derive from the DeclarativeMeta class.
Also, I disagree that you need this metaclass, what you're trying to do is
very easy using mixins, which are supported in version 0.6:
http://docs.sqlalchemy.org/en/rel_0_6/orm/extensions/declarative.html#mixing-in-columns
On Jul 3, 2013, at 12:44 AM, Ven Karri praveen.venk...@gmail.com wrote:
I use: Python 2.6 and sqlalchemy 0.6.1
This is what I am trying to do:
from sqlalchemy.types import (
Integer,
String,
Boolean
)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class SampleMeta(type):
def __new__(cls, name, bases, attrs):
attrs.update({ 'id': Column('Id', Integer, primary_key=True),
'name': Column('Name', String),
'description': Column('Description', String),
'is_active': Column('IsActive', Boolean)
})
return super(SampleMeta, cls).__new__(cls, name, bases, attrs)
class Sample(Base):
__tablename__ = 'Sample'
__table_args__ = {'useexisting': True}
__metaclass__ =
Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com wrote: On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote: The problem with using Mixins is that you need to know the definition of columns already for creating the mixin class. What I am trying to do is more like get the definition dynamically on the fly.Take a look at this: here's a simple way to add reflection events which intercept the Column and add the .key of your choice, and saves on code by making use of the existing DeferredReflection mixin instead of hand-coding it. except it doesnt work yet, give me 10 minutes. signature.asc Description: Message signed with OpenPGP using GPGMail
Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
OK here we are, had to switch approaches due to a bug with the column reflect
event, to use the aforementioned __mapper_cls__ (had the name wrong), so I
think you'll see this is a pretty open-ended way to control how something maps
as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column and
add the .key of your choice, and saves on code by making use of the existing
DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
signature.asc
Description: Message signed with OpenPGP using GPGMail
Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer mike...@zzzcomputing.comwrote:
OK here we are, had to switch approaches due to a bug with the column
reflect event, to use the aforementioned __mapper_cls__ (had the name
wrong), so I think you'll see this is a pretty open-ended way to control
how something maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column
and add the .key of your choice, and saves on code by making use of the
existing DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
--
Have a nice day !!!
--
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
I am getting ImportError for the following:
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
I use sqlalchemy 0.6.1. Is there any way I can make it work in 0.6.1 ?
On Mon, Aug 26, 2013 at 5:38 PM, Praveen praveen.venk...@gmail.com wrote:
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
OK here we are, had to switch approaches due to a bug with the column
reflect event, to use the aforementioned __mapper_cls__ (had the name
wrong), so I think you'll see this is a pretty open-ended way to control
how something maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column
and add the .key of your choice, and saves on code by making use of the
existing DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
--
Have a nice day !!!
--
Have a nice day !!!
--
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sqlalchemy group.
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
you'd need to hand-roll the deferred reflection part, there's an example in 0.7
called declarative_reflection but it might require features that aren't in
0.6.
I'd not be looking to add any kind of slick/magic systems to an 0.6 app, 0.6 is
very early in the curve for declarative techniques. upgrade it first,
otherwise stick with the hacky approaches you have.
On Aug 26, 2013, at 5:38 PM, Praveen praveen.venk...@gmail.com wrote:
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
OK here we are, had to switch approaches due to a bug with the column reflect
event, to use the aforementioned __mapper_cls__ (had the name wrong), so I
think you'll see this is a pretty open-ended way to control how something
maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column and
add the .key of your choice, and saves on code by making use of the
existing DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
--
Have a nice day !!!
--
You received this message because you are subscribed to the Google Groups
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
Could you please point me to the link where I can find the example ?
On Mon, Aug 26, 2013 at 5:41 PM, Michael Bayer mike...@zzzcomputing.comwrote:
you'd need to hand-roll the deferred reflection part, there's an example
in 0.7 called declarative_reflection but it might require features that
aren't in 0.6.
I'd not be looking to add any kind of slick/magic systems to an 0.6 app,
0.6 is very early in the curve for declarative techniques. upgrade it
first, otherwise stick with the hacky approaches you have.
On Aug 26, 2013, at 5:38 PM, Praveen praveen.venk...@gmail.com wrote:
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
OK here we are, had to switch approaches due to a bug with the column
reflect event, to use the aforementioned __mapper_cls__ (had the name
wrong), so I think you'll see this is a pretty open-ended way to control
how something maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column
and add the .key of your choice, and saves on code by making use of the
existing DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
--
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
nvm... i found it.
On Mon, Aug 26, 2013 at 5:46 PM, Praveen praveen.venk...@gmail.com wrote:
Could you please point me to the link where I can find the example ?
On Mon, Aug 26, 2013 at 5:41 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
you'd need to hand-roll the deferred reflection part, there's an example
in 0.7 called declarative_reflection but it might require features that
aren't in 0.6.
I'd not be looking to add any kind of slick/magic systems to an 0.6 app,
0.6 is very early in the curve for declarative techniques. upgrade it
first, otherwise stick with the hacky approaches you have.
On Aug 26, 2013, at 5:38 PM, Praveen praveen.venk...@gmail.com wrote:
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
OK here we are, had to switch approaches due to a bug with the column
reflect event, to use the aforementioned __mapper_cls__ (had the name
wrong), so I think you'll see this is a pretty open-ended way to control
how something maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com wrote:
The problem with using Mixins is that you need to know the definition of
columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the Column
and add the .key of your choice, and saves on code by making use of the
existing DeferredReflection mixin instead of hand-coding it.
except it doesnt work yet, give me 10 minutes.
--
Have a nice day !!!
--
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--
Have a nice day !!!
--
Have a nice day !!!
--
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Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
I tried your example in sqlalchemy 0.6 by manually plugging in api.py
library (attached) that I got from
herehttps://bitbucket.org/miracle2k/sqlalchemy/src/2d28ed97d3221a133b4b297a229deb294088affe/lib/sqlalchemy/ext/declarative/api.py?at=default
.
I get this error:
File path\to\sample_orm.py, line 33, in map_
props[v] = cls.__table__.c[k]
File path\to\lib\python2.6\sqlalchemy\util.py, line 731, in __getitem__
KeyError: 'Description'
Here's my code:
from sqlalchemy.orm import mapper
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from .api import DeferredReflection, declared_attr -- this is coming from
attached api.py file
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table Sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'Sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
# s = Session(e)
# s.add(Sample(id=1, name='some name', description='foo', is_active='foo'))
# s.commit()
On Mon, Aug 26, 2013 at 5:52 PM, Praveen praveen.venk...@gmail.com wrote:
It works only in 0.7 like you said. I can't find any way to crack this
situation in 0.6. :-(
On Mon, Aug 26, 2013 at 5:49 PM, Praveen praveen.venk...@gmail.comwrote:
nvm... i found it.
On Mon, Aug 26, 2013 at 5:46 PM, Praveen praveen.venk...@gmail.comwrote:
Could you please point me to the link where I can find the example ?
On Mon, Aug 26, 2013 at 5:41 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
you'd need to hand-roll the deferred reflection part, there's an
example in 0.7 called declarative_reflection but it might require
features that aren't in 0.6.
I'd not be looking to add any kind of slick/magic systems to an 0.6
app, 0.6 is very early in the curve for declarative techniques. upgrade it
first, otherwise stick with the hacky approaches you have.
On Aug 26, 2013, at 5:38 PM, Praveen praveen.venk...@gmail.com wrote:
Does this work in sqlalchemy 0.6.1 ?
On Mon, Aug 26, 2013 at 5:36 PM, Michael Bayer
mike...@zzzcomputing.com wrote:
OK here we are, had to switch approaches due to a bug with the column
reflect event, to use the aforementioned __mapper_cls__ (had the name
wrong), so I think you'll see this is a pretty open-ended way to control
how something maps as you're given total access to mapper() here:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy import event
Base = declarative_base()
e = create_engine(sqlite://, echo=True)
e.execute(
create table sample (
Id integer primary key,
Name varchar,
Description varchar,
IsActive varchar
)
)
class MagicMappyThing(DeferredReflection):
@declared_attr
def __mapper_cls__(cls):
def map_(cls, *arg, **kw):
props = kw.setdefault(properties, {})
for k, v in cls.__map__.items():
props[v] = cls.__table__.c[k]
return mapper(cls, *arg, **kw)
return map_
class Sample(MagicMappyThing, Base):
__tablename__ = 'sample'
__map__ = {'Id': 'id', 'Name': 'name', 'Description':
'description', 'IsActive': 'is_active'}
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
MagicMappyThing.prepare(e)
s = Session(e)
s.add(Sample(id=1, name='some name', description='foo',
is_active='foo'))
s.commit()
On Aug 26, 2013, at 5:17 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 5:16 PM, Michael Bayer mike...@zzzcomputing.com
wrote:
On Aug 26, 2013, at 4:35 PM, Praveen praveen.venk...@gmail.com
wrote:
The problem with using Mixins is that you need to know the definition
of columns already for creating the mixin class. What I am trying to do is
more like get the definition dynamically on the fly.Take a look at this:
here's a simple way to add reflection events which intercept the
Column and add the .key of your choice, and saves on code by making use of
the existing DeferredReflection mixin instead of
Re: [sqlalchemy] How to define metaclass for a class that extends from sqlalchemy declarative base ?
your metaclass must derive from the DeclarativeMeta class.
Also, I disagree that you need this metaclass, what you're trying to do is
very easy using mixins, which are supported in version 0.6:
http://docs.sqlalchemy.org/en/rel_0_6/orm/extensions/declarative.html#mixing-in-columns
On Jul 3, 2013, at 12:44 AM, Ven Karri praveen.venk...@gmail.com wrote:
I use: Python 2.6 and sqlalchemy 0.6.1
This is what I am trying to do:
from sqlalchemy.types import (
Integer,
String,
Boolean
)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class SampleMeta(type):
def __new__(cls, name, bases, attrs):
attrs.update({ 'id': Column('Id', Integer, primary_key=True),
'name': Column('Name', String),
'description': Column('Description', String),
'is_active': Column('IsActive', Boolean)
})
return super(SampleMeta, cls).__new__(cls, name, bases, attrs)
class Sample(Base):
__tablename__ = 'Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = SampleMeta
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return (%d, '%s', '%s', %r) % (self.id, self.name,
self.description, self.isactive)
And the error I am getting is this:
TypeError: Error when calling the metaclass bases
metaclass conflict: the metaclass of a derived class must be a
(non-strict) subclass of the metaclasses of all its bases
Now, if I do the same thing above by using
class Sample(object)
instead of
class Sample(Base)
it works absolutely fine.
I need to update the attributes of the class dynamically. So, I will be using
dynamic attribute and column names. And I need the above piece code to work
in order to be able to get there.
**Please help**
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