[sqlalchemy] Re: How to map columns into a tuple using SQLAlchemy?
Hi Stephen,
Not exactly what I'm looking for (unless I misunderstand you) as I'd
like to not have the individual attributes (lower, nominal, upper) in
the class directly and carry just the _limits variable.
I have a class Result as follows:
class Result:
def __init__(self):
self._limits = (None, None, None) # (lower, nominal,
upper)
def setLimits(self, limits):
self._limits = limits
...
In the database, I have a Limits table with three columns:
lower_limit, nominal, upper_limit
I'd like to map these 3 values directly into the _limits variable:
E.g.
limits_table = Table('limits', metadata, Column('id', Integer,
primary_key = True,
metadata, Column
('lower_limit', Float),
metadata, Column('nominal',
Float),
metadata, Column
('upper_limit', Float))
mapper(Result, limits_table)
By default, the Result class will
have .id, .lower_limit, .nominal, .upper_limit created. Rather than
create the 3 attributes and map to the _limits variable as you have
suggested - is there a properties= technique in the mapper or
composite column technique (w/o modifying the Result class directly)
that supports this capability?
Thanks,
Raj
On Mar 13, 3:00 am, Stephen Emslie wrote:
> You could try changing your _limit tuple to a property on the class
> that returns the tuple you want.
>
> For example:
>
> class Result(object):
>
> def get_limit(self):
> return (self.upper, self.lower, self.nominal)
> _limit = property(get_limit)
>
> Is this what you were looking for?
>
> Stephen Emslie
>
>
>
> On Wed, Mar 11, 2009 at 1:01 AM, batraone wrote:
>
> > Hi,
>
> > I'm just starting to use SQLAlchemy and hit a roadblock.
>
> > I have a class Result which contains a tuple called _limits.
> > _limits = (Upper value, lower value, nominal)
>
> > I would like to map a the table's columns directly into this tuple.
>
> > From the documentation, all I can see is columns mapping directly to
> > python attributes (I.e. Result.upper_value, Result.lower_value,..).
> > Is there a way to map the three columns directly into the tuple?
>
> > I do not want to modify the Result class and therefore cannot
> > create it as composite column type.
>
> > I'm hoping there is a syntax that states "map these 3 columns" into
> > this tuple via the mapper.
>
> > Thanks,
>
> > Raj- Hide quoted text -
>
> - Show quoted text -
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[sqlalchemy] Re: sqlalchemy 0.5.2 "'NoneType' object has no attribute 'get'" error
Hi Bruno,
I had received the same error message when I modified an attribute of
an instance. The instance was created before the map was made to the
class.
Not sure if you're doing something similar - but the sample code is in
the thread:
http://groups.google.com/group/sqlalchemy/browse_thread/thread/6f2fd14564172215
-Raj
On Mar 12, 8:57 am, "Michael Bayer" wrote:
> it means mapper compilation has failed or you're doing something
> internally on an attribute before mappers have been compiled. mappers can
> be compiled explicitly by saying compile_mappers().
>
>
>
> Bruno Zanchet wrote:
>
> > Hi all,
>
> > We're facing a weird, (apparently) hard to reproduce bug. When
> > accessing a property of an object:
> > [...]
> > sig.update('u=%s;%s;%s' % (token.user.id, token.user.yuid,
> > token.user.guid))
>
> > File "/home/y/lib/python2.5/site-packages/sqlalchemy/orm/
> > attributes.py", line 159, in __get__
> > return self.impl.get(instance_state(instance))
>
> > AttributeError: 'NoneType' object has no attribute 'get'
>
> > User is a class which extends declarative_base().
>
> > The "token.user.id" statement is triggering the exception. It's
> > SQLAlchemy 0.5.2. The same code runs just fine with 0.5.0rc4. I didn't
> > dig deeper on this, yet, but... any ideas on what might be causing
> > this?
>
> > Bruno- Hide quoted text -
>
> - Show quoted text -
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[sqlalchemy] Re: Help! More Class->Mapper confusion!
Thanks. I don't have control over the instance creation. These pre- created objects are handed down to me. I could create an adapter that maps the original class to the one that has been mapped but this is quite a bit of work as I have to manually copy over each of the source class attributes to my mapped class. I could be clever and perhaps look for common attribute names via the internal dictionary but this too seems clunky. I would think this is a common problem (augmenting a class to dump it's contents to a db but keep the original class untouched (sort of like shelve - but w/o the restore capability)). Is there a better way to handle this? Thanks, Raj On Mar 11, 2:48 pm, "Michael Bayer" wrote: > batraone wrote: > > def map(self, myfoo): > > 'Creates the map. ' > > > orm.mapper(Foo, self.t_foo, column_prefix = '_') > > > # Add foo to the database > > print dir(myfoo) # where did _name go?, _phone is there! > > > mf2 = Foo() # ok, let's create a new one. > > print dir(mf2) # same problem > > > if __name__ == '__main__': > > f = Foo() > > fs = FooStore() > > fs.map(f) > > The column_prefix wasn't being honored when the mapper checked for > existing names, this is fixed in trunk r5839. > > But also, don't create instances of the object before the class is mapped. > In particular, it's bad form to create tables and mappers inside of class > methods. Create class-level constructs like tables and mappers at the > module level, in the same scope in which you create your classes. > > > > > mf2 = Foo.Foo() # ok, let's create a new one. > > # AttributeError: 'Foo' object has no attribute > > '_sa_instance_state' > > myfoo._phone = '555-1212' # > > > if __name__ == '__main__': > > orm.clear_mappers() > > f = Foo.Foo() > > fs = FooStore() > > fs.map(f) > > don't create instances of the object before the class is mapped.- Hide quoted > text - > > - Show quoted text - --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[sqlalchemy] Help! More Class->Mapper confusion!
Hi,
OK - I ran into another thing that I do not understand about
sqlalchemy. I am a newbie, so hopefully this will be
straightforward.
There are two issues here:
ISSUE1:
I create a class called foo w/ a method called name().
I map a table that has a column called 'name' but use
the column_prefix = '_' but I do not see _name get added
to the class! But other labels, such as _phone which do
not have a corresponding method name does get added.
Here's the code:
import sqlalchemy as sa
from sqlalchemy import orm
from sqlite3 import dbapi2 as sqlite
class Foo(object):
def __init__(self):
self._myname = 'Bar'
def name(self):
return(self._myname)
class FooStore:
def __init__(self):
self.metadata = sa.MetaData()
# table to map class to
self.t_foo = sa.Table('table_foo', self.metadata,
sa.Column('id', sa.types.Integer, primary_key=True),
sa.Column('name', sa.types.String(100)),
sa.Column('phone', sa.types.String(100))
)
def map(self, myfoo):
'Creates the map. '
orm.mapper(Foo, self.t_foo, column_prefix = '_')
# Add foo to the database
print dir(myfoo) # where did _name go?, _phone is there!
mf2 = Foo() # ok, let's create a new one.
print dir(mf2) # same problem
if __name__ == '__main__':
f = Foo()
fs = FooStore()
fs.map(f)
ISSUE2: I have an object that will be given to me that I want to
store into a database. The class definition is located in a package.
When I map this class to a table and set the attribute - I get
an exception:
AttributeError: 'NoneType' object has no attribute 'set'
This can be seen by modifying the above example - where I put
Foo into a package called 'foo':
import sqlalchemy as sa
from sqlalchemy import orm
from sqlite3 import dbapi2 as sqlite
import sys
import foo.Foo as Foo
class FooStore:
def __init__(self):
self.metadata = sa.MetaData()
# table to map class to
self.t_foo = sa.Table('table_foo', self.metadata,
sa.Column('id', sa.types.Integer, primary_key=True),
sa.Column('name', sa.types.String(100)),
sa.Column('phone', sa.types.String(100))
)
def map(self, myfoo):
'Creates the map. te is the test engine'
orm.mapper(Foo.Foo, self.t_foo, column_prefix = '_')
# Add foo to the database
try:
myfoo._phone = '555-1212' # exception is thrown!
except:
#AttributeError: 'NoneType' object has no attribute 'set'
print sys.exc_info()
mf2 = Foo.Foo() # ok, let's create a new one.
# AttributeError: 'Foo' object has no attribute
'_sa_instance_state'
myfoo._phone = '555-1212' #
if __name__ == '__main__':
orm.clear_mappers()
f = Foo.Foo()
fs = FooStore()
fs.map(f)
What's the right way to adapt this class to a table?
Thanks!
-Raj
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[sqlalchemy] How to map columns into a tuple using SQLAlchemy?
Hi, I'm just starting to use SQLAlchemy and hit a roadblock. I have a class Result which contains a tuple called _limits. _limits = (Upper value, lower value, nominal) I would like to map a the table's columns directly into this tuple. >From the documentation, all I can see is columns mapping directly to python attributes (I.e. Result.upper_value, Result.lower_value,..). Is there a way to map the three columns directly into the tuple? I do not want to modify the Result class and therefore cannot create it as composite column type. I'm hoping there is a syntax that states "map these 3 columns" into this tuple via the mapper. Thanks, Raj --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[sqlalchemy] How to map columns into a tuple using SQLAlchemy?
Hi, I'm just starting to use SQLAlchemy and hit a roadblock. I have a class Result which contains a tuple called _limits. _limits = (Upper value, lower value, nominal) I would like to map a the table's columns directly into this tuple. >From the documentation, all I can see is columns mapping directly to python attributes (I.e. Result.upper_value, Result.lower_value,..). Is there a way to map the three columns directly into the tuple? I do not want to modify the Result class and therefore cannot create it as composite column type. I'm hoping there is a syntax that states "map these 3 columns" into this tuple via the mapper. Thanks, Raj --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
