Simon, your idea about putting together a script is a good one. Please see
the attached. I think all these errors are related but I'm scratching my
head about what the problem is.
The reason I use self.creator[0] versus self.creator is for aesthetics.
And, to your point about creator not being a list, SQLAlchemy is treating
creator as a list-like object. Since any company can only have one creator,
I wasn't concerned about indexing creator[0].
>>> a=session.query(Company).first()
>>> a
Company1, created by mike
rather than
>>> a=session.query(Company).first()
>>> a
Company1, created by [mike]
>>> a.creator
[mike]
More info on creator:
>>> type(a.creator)
<class 'sqlalchemy.orm.collections.InstrumentedList'>
>>> type(a.creator[0])
<class '__main__.Creator'>
Chris
On Wednesday, August 14, 2013 6:18:51 AM UTC-4, Simon King wrote:
>
> I think you may be confused about the relationship properties you have
> here. As far as I can tell, a Creator can have many companies, but
> each Company has only one creator, correct? So Company.creator should
> only ever be an instance of Creator (or None), whereas
> Creator.companies should be a list.
>
> In your __repr__ example:
>
> class Creator(Base):
> def __repr__(self):
> return '%s' % self.creator
>
> class Company(Base):
> def __repr__(self):
> return '%s, created by %s' % (self.company, self.creator[0])
>
> Why are you using "self.creator[0]" here? self.creator is not a list,
> it should either be an instance of Creator, or None.
>
> Overriding __repr__ is also a good way to make debugging difficult.
> For example, if you had a list of Creator instances and you printed
> them at the python prompt, it would just look like a list of strings.
> When I want extra information from __repr__, I normally write it
> something like this:
>
> def __repr__(self):
> classname = type(self).__name__
> return '<%s name=%r>' % (classname, self.name)
>
> In your second example:
>
> >>> a=session.query(Creator).first()
> >>> a[0].companies
> >>> a.companies
>
> Query.first() returns a single value, not a list. So typing "a[0]"
> doesn't make any sense.
>
> Please try to create a self-contained script that demonstrates your
> problem. Here is a good example:
>
> https://groups.google.com/d/msg/sqlalchemy/jQtIRJXVfH8/LgwX-bomEIQJ
>
> Thanks,
>
> Simon
>
> On Wed, Aug 14, 2013 at 2:45 AM, <[email protected] <javascript:>> wrote:
> > I'm afraid there are still some bugs in here that hopefully you can help
> > with.
> >
> > class Creator(Base):
> > __tablename__ = "creators"
> > id = Column(Integer, primary_key = True)
> > company_id = Column(Integer, ForeignKey('companies.id'))
> > creator = Column(String(100), nullable=False, unique=True)
> > def __init__(self, creator):
> > self.creator = creator
> > def __repr__(self):
> > return '%s' % self.creator # otherwise returns a single entry
> list
> > for some reason (e.g. would display [user])
> >
> > class Company(Base):
> > __tablename__ = "companies"
> > id = Column(Integer, primary_key = True)
> > company = Column(String(100), unique=True, nullable=False) #might
> want
> > to revise string sizes at some point
> > creator = relationship("Creator", backref="companies",
> cascade="all")
> > def __init__(self, company, creator):
> > self.company = company
> > #self.creator.append(Creator(creator))
> > existing_creator =
> > session.query(Creator).filter_by(creator=creator).first()
> > #self.creator.append(existing_creator or Creator(creator))
> > if existing_creator:
> > print True
> > self.creator.append(existing_creator)
> > else:
> > self.creator.append(Creator(creator))
> > def __repr__(self):
> > return '%s, created by %s' % (self.company, self.creator[0])
> >
> >
> >
> > 1) Weird __repr__ error:
> >
> > class Creator(Base):
> > def __repr__(self):
> > return '%s' % self.creator
> >
> > class Company(Base):
> > def __repr__(self):
> > return '%s, created by %s' % (self.company, self.creator[0])
> >
> >>>> c=Company("Company1", "mike")
> >>>> session.add(c)
> >>>> c=Company("Company2", "mike")
> > True
> >>>> session.add(c)
> >>>> c=Company("Company3", "john")
> >>>> session.add(c)
> >>>> c=Company("Company4", "mike")
> > True
> >>>> session.add(c)
> >>>> session.query(Company).all()
> > [Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File "<stdin>", line 17, in __repr__
> >
> >
> > However, if I divide the query lines among every add() statement, there
> is
> > no __repr__ error.
> >
> >>>> c=Company("Company1", "mike")
> >>>> session.add(c)
> >>>> session.query(Company).all()
> > [Company1, created by mike]
> >>>> c=Company("Company2", "mike")
> > True
> >>>> session.add(c)
> >>>> session.query(Company).all()
> > [Company1, created by mike, Company2, created by mike]
> >>>> c=Company("Company3", "john")
> >>>> session.add(c)
> >>>> session.query(Company).all()
> > [Company1, created by mike, Company2, created by mike, Company3, created
> by
> > john]
> >>>> c=Company("Company4", "mike")
> > True
> >>>> session.add(c)
> >>>> session.query(Company).all()
> > [Company1, created by mike, Company2, created by mike, Company3, created
> by
> > john, Company4, created by mike]
> >
> >
> > 2) Creator.companies only shows the most recently added company:
> >
> >>>> session.query(Company).all()
> > [Company1, created by mike, Company2, created by mike, Company3, created
> by
> > john, Company4, created by mike]
> >>>> session.query(Creator).all()
> > [mike, john]
> >>>> a=session.query(Creator).first()
> >>>> a[0].companies
> >>>> a.companies
> > Company4, created by mike
> >
> >
> > 3) Weird Company.creator error:
> >
> >>>> session.query(Company).all()
> > [Company1, created by mike, Company2, created by mike, Company3, created
> by
> > john, Company4, created by mike]
> >>>> session.query(Company.creator).all()
> > [(False,), (False,), (False,), (False,), (True,), (False,), (False,),
> > (True,)]
> >>>> a=session.query(Company).first()
> >>>> a.creator
> > [mike]
> >
> > Anyone have any ideas?
> >
> > --
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>
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from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref
from sqlalchemy.orm import sessionmaker
engine = create_engine('mysql://project:project@localhost/cbff', echo=False) # Toggle echo to show db interactions
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()
class Creator(Base):
__tablename__ = "creators"
id = Column(Integer, primary_key = True)
company_id = Column(Integer, ForeignKey('companies.id'))
creator = Column(String(100), nullable=False, unique=True)
def __init__(self, creator):
self.creator = creator
def __repr__(self):
return '%s' % self.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
existing_creator = session.query(Creator).filter_by(creator=creator).first()
if existing_creator:
self.creator.append(existing_creator)
else:
self.creator.append(Creator(creator))
def __repr__(self):
return '%s, created by %s' % (self.company, self.creator)
Base.metadata.create_all(engine)
print"""
Bug #1
Session.query() affects __repr__ for some reason.
------
"""
# Output:
# Case #1
# >>> c=Company("Company1", "mike")
# >>> session.add(c)
# >>> c=Company("Company2", "mike")
# >>> session.add(c)
# >>> c=Company("Company3", "john")
# >>> session.add(c)
# >>> c=Company("Company4", "mike")
# >>> session.add(c)
# >>> session.query(Company).all()
# [Company1, created by [], Company2, created by [], Company3, created by [john], Company4, created by [mike]]
# Case #2
# >>> c=Company("Company1", "mike")
# >>> session.add(c)
# >>> session.query(Company).all()
# [Company1, created by [mike]]
# >>> c=Company("Company2", "mike")
# >>> session.add(c)
# >>> session.query(Company).all()
# [Company1, created by [mike], Company2, created by [mike]]
# >>> c=Company("Company3", "john")
# >>> session.add(c)
# >>> session.query(Company).all()
# [Company1, created by [mike], Company2, created by [mike], Company3, created by [john]]
# >>> c=Company("Company4", "mike")
# >>> session.add(c)
# >>> session.query(Company).all()
# [Company1, created by [mike], Company2, created by [mike], Company3, created by [john], Company4, created by [mike]]
print "Case #1"
c=Company("Company1", "mike")
session.add(c)
c=Company("Company2", "mike")
session.add(c)
c=Company("Company3", "john")
session.add(c)
c=Company("Company4", "mike")
session.add(c)
session.query(Company).all()
session.rollback()
print "Case #2"
c=Company("Company1", "mike")
session.add(c)
session.query(Company).all()
c=Company("Company2", "mike")
session.add(c)
session.query(Company).all()
c=Company("Company3", "john")
session.add(c)
session.query(Company).all()
c=Company("Company4", "mike")
session.add(c)
session.query(Company).all()
print"""
Bug #2
Creator.companies only shows the most recently added company, when it should return a list of all companies linked to a particular creator
"""
# Output:
# >>> session.query(Company).all()
# [Company1, created by mike, Company2, created by mike, Company3, created by john, Company4, created by mike]
# >>> session.query(Creator).all()
# [mike, john]
# >>> a=session.query(Creator).first()
# >>> a.companies
# Company4, created by mike
session.query(Company).all()
session.query(Creator).all()
a=session.query(Creator).first()
a.companies
print """
Bug #3
Immediately after the above, doing session.query(Company.all() again throws an error message.
NOTE: I tried to replicate this error after putting this script together and couldn't reproduce it. I do not know why this is.
"""
# Output:
# >>> session.query(Company).all()
# [Traceback (most recent call last):
# File "<stdin>", line 1, in <module>
# File "<stdin>", line 14, in __repr__
# IndexError: list index out of range
session.query(Company).all()
print """
Bug #4
The above errors seems to be linked to the following odd behavior
"""
# Output:
# >>> session.query(Company.creator).all()
# [(False,), (False,), (False,), (False,), (True,), (False,), (False,), (True,)]
session.query(Company.creator).all()
