It's not the append that's causing the error, it's the fact that you're
creating a new Creator() instance, which ultimately results in an INSERT
statement being issued.
You want to append a Creator instance to `company.creator`, but you don't
necessarily want to make a new Creator every time you instantiate a Company. If
a Creator with the given name already exists, you'll want use that instead.
So, roughly:
class Company(Base):
__tablename__ = "companies"
id = Column(Integer, primary_key = True)
company = Column(String(100), unique=True, nullable=False)
creator = relationship("Creator", backref="companies", cascade="all")
def __init__(self, company, creator):
self.company = company
existing_creator = DBSession(Creator).query.filter_by(name=creator).first()
self.creator.append(existing_creator or Creator(creator))
--
Tim Van Steenburgh
On Monday, August 12, 2013 at 9:41 PM, [email protected] wrote:
> Sorry I don't understand what you're trying to say.
>
> If the Creator already exists, and I'm to append it again, isn't that the
> same as what my code is currently doing? (That is, appending in every
> instance.) I don't see how this wouldn't result in the same error message.
>
> And what would it mean to create a new one and append that? I don't know what
> this code would look like.
>
> Apologies if I'm being dense.
>
> On Monday, August 12, 2013 9:33:31 PM UTC-4, Tim wrote:
> > In `Company.__init__()`, instead of blindly creating a new `Creator`
> > instance, you need to first query for an existing Creator with that name.
> > If it exists, append it, otherwise, create a new one and append that.
> >
> > --
> > Tim Van Steenburgh
> >
> >
> > On Monday, August 12, 2013 at 9:26 PM, [email protected] (javascript:) wrote:
> >
> > > I have another question about a piece of code that I posted the other
> > > day. Namely, I have a one-to-many relationship between Creator and
> > > Company. A Creator can have a relationship with multiple Companies but
> > > any one Company can have a relationship with only one Creator.
> > >
> > > class Company(Base):
> > > __tablename__ = "companies"
> > > id = Column(Integer, primary_key = True)
> > > company = Column(String(100), unique=True, nullable=False)
> > > creator = relationship("Creator", backref="companies", cascade="all")
> > >
> > >
> > > def __init__(self, company, creator):
> > > self.company = company
> > > self.creator.append(Creator(creator))
> > >
> > > class Creator(Base):
> > > __tablename__ = "creators"
> > >
> > > company_id = Column(Integer, ForeignKey('companies.id
> > > (http://companies.id/)'))
> > > creator = Column(String(100), nullable=False, unique=True)
> > >
> > > def __init__(self, creator):
> > > self.creator = creator
> > >
> > >
> > > So, to create a Company, the code calls company = Company(<company name>,
> > > <creator name>) and that in turn calls Creator().
> > >
> > > The problem is that the Companies get added one by one, and if a new
> > > company being entered has a Creator with a name of a preexisting company,
> > > SQLalchemy errors due to the unique=True flag:
> > >
> > > sqlalchemy.exc.IntegrityError: (IntegrityError) (1062, "Duplicate entry
> > > 'Viking' for key 'creator'") 'INSERT INTO creators (company_id, creator)
> > > VALUES (%s, %s)' (17L, u'Viking')
> > >
> > > If unique=True isn't enabled, it will create another Creator of the same
> > > name. Instead, the code should reflect the additional Company assigned to
> > > this particular Creator. How might I go about fixing this?
> > >
> > > Thanks!
> > >
> > > --
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> > >
> > >
> >
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