Shuo Yang wrote:
> If I had:
>
> class Class(object):
> pass
>
> class Student(object):
> def __init__(self, class):
> self.class = class
>
> What's the intended way to add a student record that associates to a
> class? Could I do something like this?
> class = Class('english')
> student = Student(class=class)
>
> It doesn't work when I do objectstore.commit(). Only a "none" is
> inserted for foreign key on student table.
>
> --
> ---------------------------------------------------------------------------------------------------
>
> John S. Yang
Hello John,
I am also just getting into Sqlalchemy, and in my first project I will
be doing something like your example, so I worked through it:
First, I suggest you never use a Python reserved word like 'class' as an
identifier. Even though it might be legal in the place you used it, it
is going to create confusion down the road.
####
from sqlalchemy import *
engine = create_engine('mysql',
{'db':'sc',
'user':'root'},
echo=True
)
klasses = Table('klasses', engine,
Column('klass_id', Integer, primary_key=True),
Column('teacher_name', String(50), nullable=False)
)
students = Table('students', engine,
Column('student_id', Integer, primary_key=True),
Column('student_name', String(16), nullable=False),
Column('klass_id', Integer,
ForeignKey('klasses.klass_id'))
)
class Klass(object):
pass
class Student(object):
def __init__(self, klass=None):
self.klass = klass
Klass.mapper = mapper(Klass, klasses)
Student.mapper = mapper(Student, students,
properties = {
'klass' : relation(Klass.mapper)
}
)
## ipython session
In [2]: k = Klass()
In [3]: k.teacher_name = 'Elephant'
In [4]: s = Student(klass=k)
In [5]: s.student_name = 'Marin'
In [6]: objectstore.commit()
INSERT INTO klasses (teacher_name) VALUES (%s)
['Elephant']
INSERT INTO students (student_name, klass_id) VALUES (%s, %s)
['Marin', 1L]
In [7]: s.klass.klass_id
Out[7]: 1L
In [8]: s.klass.teacher_name
Out[8]: 'Elephant'
###
-- Wade Leftwich
Ithaca, NY
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