How to clone a sqlalchemy db object with new primary key

Question

I want to clone a SQLAlchemy object:

I tried:

product_obj = products.all()[0] #here products is service name  product_obj.product_uid = 'soemthing' #here product_uid is the pk of product model  products.save(product_obj) 

but it just updates the old object.

Here is the code of products.save function:

class Service(object):          __model__ = None         def save(self, model):             self._isinstance(model)             db.session.add(model)             db.session.commit()             return model 

Answer 1

This should work:

product_obj = products.all()[0]  db.session.expunge(product_obj)  # expunge the object from session make_transient(product_obj)  # http://docs.sqlalchemy.org/en/rel_1_1/orm/session_api.html#sqlalchemy.orm.session.make_transient  product_obj.product_uid = 'something' db.session.add(product_obj) 

Answer 2

For sqlalchemy 1.3 I ended up using a helper function.

1. It copies all the non-primary-key columns from the input model to a new model instance.
2. It allows you to pass data directly as keyword arguments.
3. It leaves the original model object unmodified.

def clone_model(model, **kwargs):     """Clone an arbitrary sqlalchemy model object without its primary key values."""     # Ensure the model’s data is loaded before copying.     model.id      table = model.__table__     non_pk_columns = [k for k in table.columns.keys() if k not in table.primary_key.columns.keys()]     data = {c: getattr(model, c) for c in non_pk_columns}     data.update(kwargs)      clone = model.__class__(**data)     db.session.add(clone)     db.session.commit()     return clone 

With this function you can solve the above problem using:

product_obj = products.all()[0]  # Get the product from somewhere. cloned_product_obj = clone_model(product_obj, product_uid='something') 

Depending on your use-case you might want to remove the call to db.session.commit() from this function.

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This answer is based on https://stackoverflow.com/a/13752442/769486 (How to get a model’s columns?) and How do I get the name of an SQLAlchemy object's primary key? (How do I get a model’s primary keys?).