Re: [sqlalchemy] Repetitive Fields in declarative
On Fri, Aug 19, 2011 at 9:23 AM, Mark Erbaugh wrote:
>
> On Aug 19, 2011, at 10:41 AM, Michael Bayer wrote:
>
> > Id use a mixin so that a superclass can be generated in a data driven
> manner:
> >
> >
> > MyCols = type("MyCols", (object, ), dict(("field%d" % i, Column(Integer))
> for i in xrange(1, 10)))
>
If you are going to do this a lot, it can be a pain with declarative. I
developed a framework that I used, based on ORM, which uses an explicit
_makeTable() and _mapTable() objects that I call in order to create and map
the tables. Since these are python methods, I can use any kind of python
iteration or code I want to decide what columns to create. It is a pretty
flexible model. Example conceptual code:
class Database(object):
table_args = { 'mysql_engine' : 'InnoDB' }
schema = "database_name"
def __init__(self,dbclasses=[]):
self.metadata = MetaData()
self.engine = ... (set up engine, etc.)
self.dbclasses = dbclasses
for c in self.dbclasses:
c._makeTable(self,self.engine)
cls.__table__.create(bind=self.engine,checkfirst=True)
for c in self.dbclasses:
c._mapTable(self)
class FooRecord(object):
@classmethod
def _makeTable(cls,db,engine):
cls.db = db
cls.__table__ = Table('foo', db.metadata,
Column('x'),
Column('y'),
**cls.table_args,
schema=cls.schema
etc.)
@classmethod
def _mapTable(cls,db):
mapper(cls, cls.__table__, properties={ ... })
db = Database([FooRecord])
You may find a model like this easier to use to create dynamically-generated
tables. The point here is that SQLAlchemy is sufficiently flexible so that
if declarative doesn't meet your needs or is a bit cumbersome for what you
want to do, you can just start at the ORM (below declarative) level and
build up a framework that works for you.
Regards,
Daniel
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Re: [sqlalchemy] Repetitive Fields in declarative
On Aug 19, 2011, at 10:41 AM, Michael Bayer wrote:
> Id use a mixin so that a superclass can be generated in a data driven manner:
>
>
> MyCols = type("MyCols", (object, ), dict(("field%d" % i, Column(Integer)) for
> i in xrange(1, 10)))
>
> class MyClass(MyCols, Base):
>...
>
> otherwise if you want to go the append_column() route, you can just tack them
> on the class, declarative will call append_column() as well as
> mapper.add_property():
>
> for name, col in ("field%d" % i, Column(Integer)) for i in xrange(1, 10)):
>setattr(MyClass, name, col)
Michael,
Thanks for the info.
Mark
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Re: [sqlalchemy] Repetitive Fields in declarative
On Aug 18, 2011, at 6:06 PM, Mark Erbaugh wrote:
> I want to create a table that has several similar fields. For example, assume
> the fields are field1, field2, ...
>
> Is there a way in the declarative class that I can do something like:
>
> for i in range(10):
> 'field%d' % i = Column( ... )
>
Id use a mixin so that a superclass can be generated in a data driven manner:
MyCols = type("MyCols", (object, ), dict(("field%d" % i, Column(Integer)) for i
in xrange(1, 10)))
class MyClass(MyCols, Base):
...
otherwise if you want to go the append_column() route, you can just tack them
on the class, declarative will call append_column() as well as
mapper.add_property():
for name, col in ("field%d" % i, Column(Integer)) for i in xrange(1, 10)):
setattr(MyClass, name, col)
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Re: [sqlalchemy] Repetitive Fields in declarative
On Aug 18, 2011, at 7:01 PM, Mark Erbaugh wrote:
>
> On Aug 18, 2011, at 6:06 PM, Mark Erbaugh wrote:
>
>> want to create a table that has several similar fields. For example, assume
>> the fields are field1, field2, ...
>>
>> Is there a way in the declarative class that I can do something like:
>>
>> for i in range(10):
>> 'field%d' % i = Column( ... )
>>
>>
>> Thanks,
>> Mark
>
>
> Figured it out:
>
> after the class definition:
>
> for i in range(10):
> .__table__.append_column(Column('field%d' % i, ...))
I guess not: while the above code adds the fields to the database table, it
doesn't add them as named data members of the class. Here's my latest effort:
class Preferences:
...
for i in range(10):
setattr(Preferences, 'field%d' % i, Column(...
This also answers my question about relationships
setattr(Preferences 'relationship%d' % i, relationship(...
Mark
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Re: [sqlalchemy] Repetitive Fields in declarative
Me again (see below):
On Aug 18, 2011, at 7:01 PM, Mark Erbaugh wrote:
>
> On Aug 18, 2011, at 6:06 PM, Mark Erbaugh wrote:
>
>> want to create a table that has several similar fields. For example, assume
>> the fields are field1, field2, ...
>>
>> Is there a way in the declarative class that I can do something like:
>>
>> for i in range(10):
>> 'field%d' % i = Column( ... )
>>
>>
>> Thanks,
>> Mark
>
>
> Figured it out:
>
> after the class definition:
>
> for i in range(10):
> .__table__.append_column(Column('field%d' % i, ...))
Some of the fields that I am adding this way are foreign keys to another table.
Is there a way to specify a relationship based on these foreign key fields?
Mark
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Re: [sqlalchemy] Repetitive Fields in declarative
On Aug 18, 2011, at 6:06 PM, Mark Erbaugh wrote:
> want to create a table that has several similar fields. For example, assume
> the fields are field1, field2, ...
>
> Is there a way in the declarative class that I can do something like:
>
> for i in range(10):
> 'field%d' % i = Column( ... )
>
>
> Thanks,
> Mark
Figured it out:
after the class definition:
for i in range(10):
.__table__.append_column(Column('field%d' % i, ...))
Mark
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[sqlalchemy] Repetitive Fields in declarative
I want to create a table that has several similar fields. For example, assume the fields are field1, field2, ... Is there a way in the declarative class that I can do something like: for i in range(10): 'field%d' % i = Column( ... ) Thanks, Mark -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
