Hello,
This is the first time I try an ORM, and I chose SQLAlchemy, which is popular
amongst pythonistas.
Since I am a complete beginner, here's my beginner's two cents question :
Suppose you have a very basic model like this (pseudo code) :
User(firstname,lastname,nick,ManyToOne(city))
City(name)
Suppose I want to add a new user:
user = User("John","Doe","jd", WhatToPutHere ?)
I whish I could write something like this :
user = User("John","Doe","jd", City("New Jersey"))
Where City will first fetch for a city named New Jersey in the database and
return it if it exists, or create a new one (in the database) and return it.
So I thought maybe I could have a helper function like this :
def city(name):
return City.query.filter_by(name=name).first() or City(name=name)
and then :
user = User("John","Doe","jd",city("New Jersey"))
But how can I be sure that the city of New Jersey will be inserted before the
user in the database so that the new user row will get the proper city id ?
So I figured to rewrite the city helper function like this :
def city(name):
theCity = City.query.filter_by(name=name).first()
if not theCity :
theCity = City(name=name)
session.commit() # to be sure it will be inserted before the user
return theCity
In the videostore example I saw an interresting use of the @classmethod
decorator, which may be useful to define city as a static method of the City
class.
I need your advice. Is this a good way to tackle to problem ? how does your
code look like ?
Y.Chaouche
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