I wonder if one can also do this with Declarative Base classes using `type`
construction? Like, to dynamically create a Declarative Class from some
pre-defined namespace dicts:
Base = declarative_base()
metas = [{'__tablename__': 'footable'}, ...]
columns = [{ 'key': 'field1', 'type': Text}, ...]
cls_names = ['Foo', ...]
clses = {name: type(name, Base, **dict(metas[i], **{ c['key']:
Column(c['type']) for c in columns}) for i, name in enumerate(cls_names)}
Now I should have a dict of classes I can instantiate by class name:
new_foo = clses['Foo'](...)
My particular use case is that I can overload some of the namespaces, to
decouple the model namespace (the class attributes) from SQLAlchemy, but my
instance will still have the predefined attribute names - I am storing data
in either the database or a flatfile and I instantiate either a SQLAlchemy
declarative object or a generic `object` depending on a flag; after
instancing (whether to run a query or parse the flatfile), my application
can refer to the object attributes regardless of where the data comes from.
On Monday, March 26, 2018 at 2:42:51 PM UTC-4, Mike Bayer wrote:
>
> On Mon, Mar 26, 2018 at 1:54 PM, Prashanth Budihal
> <[email protected] <javascript:>> wrote:
> > I have this project(stock market data) where I need many tables(200+)
> and
> > each one will receive fresh data inserts periodically(every 5 minutes).
> I
> > have gone thru couple of tutorials about sqlalchemy ORM and they all
> show
> > how to create a single table and do few inserts. But if I have to create
> > 200+ tables then should I create/type manually 200+ mapped classes ?
> Thats
> > impractical isnt it ? I face same hurdle while doing INSERTS. Can
> anybody
> > here give me a hint atleast how to go about this ? Which part of
> sqlalchemy
> > addresses this hurdle. I admit I am a newbie to sql and sqlalchemy so
> please
> > bear with me if there is already a solution and I havent studied it yet.
> > Thanks in advance.
>
> Python is a fully dynamic language so if you needed 200 classes given
> a list of 200 names, you would never have to "type" that manually.
> However if this is a really simple case then just use core:
>
> my_twohundred_names = [ ... names ....]
>
> with engine.connect() as conn:
> for name in my_twohundred_names:
> t = Table(name, MetaData(), Column('q', Integer), Column('p',
> Integer), ... )
> conn.execute(t.insert(), {"q": 5, "p": 10})
>
> something like that.
>
> if these tables have all kinds of different columns you can reflect them:
>
>
> my_twohundred_names = [ ... names ....]
>
> with engine.connect() as conn:
> for name in my_twohundred_names:
> t = Table(name, MetaData(), autoload_with=conn)
> conn.execute(t.insert(), {"q": 5, "p": 10})
>
> but you need to know what the columns are that you are inserting.
>
>
> >
> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
> > To post example code, please provide an MCVE: Minimal, Complete, and
> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> > description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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