Michael,
Do you ever sleep?
I am not sure I get your point. How do I set up a common "Base".
I could do Base= Declarative_base()
from a import A (or * not sure how this differs in this case)
from b import B (or *)
If I do not declare Base in module "a" I get an Import Error on class A(Base),
the same for importing b.
This gets even more complicated when Base should be build from classes defined
across modules.
at the end there is one main.py importing all modules and this should be able
to define the "Main Base".
Any suggestions on how to tackle this. I know have multiple modules and am
glueing everything together. This even gets more problematic with Inheritance.
one solution could be..
from a import A, BaseA
from b import B, BaseB
Base = declarative_base()
metadata - BaseA.metadata + BaseB.metadata
metadata.create_all(engine)
What I do not get is how the mapper is configured. Normally with declarative
Base it is not used in "Production fase" for as far as I can see.....
The mapper is part of the Class right? and session does not use Base at all?
but gets it when needed -> Session.query(A)..... ?
Or am I totally wrong on this?
Can I something like this:
from a import * (imports class A and the declarative_base BaseA)
Base = declarative_base()
class C(Base):
.......
BaseForB = declarative_base(metadata=BaseA)
class B(BaseForB)
Mixin classes are of type object so there is no issue since @declared_attr etc
works....
class D(Base,mixinclass) works without a Base at all so there is no Issue....
Am I right? in understanding your comments on my first mail in this topic?
Martijn
On Feb 8, 2011, at 7:46 PM, Michael Bayer wrote:
>
> On Feb 8, 2011, at 1:19 PM, Martijn Moeling wrote:
>
>> Hi,
>>
>> I am having a small issue with multiple python modules and declarative...
>>
>> I might miss something but....
>>
>> Consider:
>>
>> a.py:
>>
>> 8<-------------------------------
>> Base = declarative_base()
>>
>> class A(Base):
>> ...
>> 8<-------------------------------
>>
>> b.py
>> Base = declarative_base()
>>
>> class B(Base):
>> ...
>> 8<-------------------------------
>>
>> c.py
>> Base = declarative_base()
>>
>> class C(Base):
>> ...
>> 8<-------------------------------
>>
>> d.py
>>
>> Base = declarative_base()
>>
>> from A import * # imports base....
>> from B import * # imports base....
>> from C import * # imports base....
>>
>> Class D1(Base)
>> ...
>>
>> Class D2(A)
>> ...
>>
>>
>> in d.py I want to create:
>>
>> def create_tables(engine):
>> metadata= Base.metadata
>> metadata.create_all(engine)
>>
>>
>> Is there any way to properly "add" the metadata from the imported modules in
>> d.py to the Base.metadata during the import......?
>> Think of modules a,b,c and d are together in a package and d is imported
>> with similar packages into something bigger....
>
> Usually the convention is that all modules in an application share the same
> declarative base object (i.e. Base). If you wanted multiple Base objects
> but have them share a common MetaData, you can declare the MetaData up front,
> then create each Base using declarative_base(metadata=my_metadata).
> Otherwise if you're really looking to merge together multiple MetaData
> objects, that's not really in the API right now in a clean way, you'd perhaps
> call .tometadata() on each Table object but that's really not what I would do
> here - it copies the whole Table object and isn't really for a use case like
> this. If you can at least have a common MetaData object, or better a common
> Base object, that would be the best way to go.
>
>
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