mr wrote:
> Hejhej,
> first I'd like to thank the developers of SQLAlchemy for their great
> effort. The library works like a treat and is well documented. It's a
> pleasure working with it...
> Nevertheless I've currently run into a problem when trying to create
> classes that are based on read-only reflection from existing database
> tables. Here *read-only* means that I have a database table with fixed
> contents that I'm not going to change in application. However, I need
> this table and its contents to create other objects.
> Let's assume we have a table *foos* with a number of rows - each of
> them representing a distinct *foo*. There is the usual id column
> *foo_id*, then there's *foo_name* and *foo_key*. I've been able to
> come up with the following code to that uses reflection to derive the
> table metadata.
>
> engine = create_engine('postgresql://...')
> Base = declarative_base()
>
> class Foo(Base):
> __tablename__ = 'foos
> __autoload__ = True
> __table_args__ = {'autoload_with': engine}
>
> def __init__(self):
> pass
>
> Now when I create a foo object with f = Foo() I can see all columns of
> the existing table by doing something like:
> print f.metadata.tables[f.__tablename__].columns
>
> What I want to do now is to initialize a *foo*-object by specifying
> *foo_key* in the constructor so that I have exactly the one distinct
> row containing *foo_key* at my disposal for further processing.
>
> def __init__(self, foo_key):
> ...
>
> However I was not able to do this... Am I missing something here? Or
> did anybody else had a similar problem and was able to solve it...
> Thank you very much in advance.
I think you are looking for this
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/UniqueObject
> Regards,
> Markus
>
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