Question

I’m trying to create a small IRC connection with Python, now I want it to be able to connect to multiple servers so I created a server class that will connect to the server, I wanted to save the servers onto a db as well so I used sqlalchemy to do that. This is the init on the server class

def __init__(self, server_name, server_address, server_port=6667):
        threading.Thread.__init__(self)
        self.server_name = server_name
        self.server_address = server_address
        self.server_port = server_port

Now the weird part is that it actually works if I call create a class “manually” like this

bla = IRCLib.connect("local","127.0.0.1")

this way it connects and there is no problem at all, however when I load the class through SQLAlchemy like this

bla = db.BaseService.session.query(IRCLib.server)
res = bla.all()
res[0].connect()

I get this error

raise RuntimeError("thread.__init__() not called")

Now the connect and run function on the class are this

def connect(self):
        self.irc = socket.socket ( socket.AF_INET, socket.SOCK_STREAM )
        self.irc.connect ( ( self.server_address, self.server_port ) )
        self.irc_file = self.irc.makefile("rb")
        self.start()

    def run(self):
        print "in run"
        self.irc.send ( 'NICK Test\r\n' )
        self.irc.send ( 'USER lsb lsb lsb :lsb\r\n' )
        while True:
            data = self.irc_file.readline()
            print data

I’m really not sure what I can do to get it to work with SQLAlchemy, because like I said, it works if I do it manually.

Thanks

Answer 1

The __init__() method isn’t called when SQLAlchemy loads an object from the database (docs: http://docs.sqlalchemy.org/en/rel_0_7/orm/mapper_config.html#constructors-and-object-initialization). To perform a task each time an object is loaded, use the @orm.reconstructor hook described in that section:

from sqlalchemy import orm

class MyMappedClass(object):
    def __init__(self, data):
        self.data = data
        # we need stuff on all instances, but not in the database.
        self.stuff = []

    @orm.reconstructor
    def init_on_load(self):
        self.stuff = []