How do I set a callback in Python?

[catsclaw]

I can't for the life of me figure out how to set a callback in
Python. I have a class, which wraps another class. The second class
needs a callback assigned. I don't want to use globals for it.
Here's what I'd like to do:

class MyWrapper:
def get_login(self, username):
return self.user, self.pass

def __init__(self, user, pass):
self.user = user
self.pass = pass

self.client = Client("connection string")
self.client.callback_login = get_login

.... but obviously, the Client class, when it calls the callback,
doesn't pass a reference to the "self" object. How do I do this?

-- Chris

[Rob Williscroft]

catsclaw wrote in news:d797403a-e492-403f-933a-bd18ef53d5c0
@k13g2000hse.googlegroups.com in comp.lang.python:

I can't for the life of me figure out how to set a callback in
Python. I have a class, which wraps another class. The second class
needs a callback assigned. I don't want to use globals for it.
Here's what I'd like to do:

class MyWrapper:
def get_login(self, username):
return self.user, self.pass

def __init__(self, user, pass):
self.user = user
self.pass = pass

self.client = Client("connection string")
self.client.callback_login = get_login

... but obviously, the Client class, when it calls the callback,
doesn't pass a reference to the "self" object. How do I do this?

use:
self.client.callback_login = self.get_login
Rob.
--
http://www.victim-prime.dsl.pipex.com/

[Diez B. Roggisch]

catsclaw schrieb:

I can't for the life of me figure out how to set a callback in
Python. I have a class, which wraps another class. The second class
needs a callback assigned. I don't want to use globals for it.
Here's what I'd like to do:

class MyWrapper:
def get_login(self, username):
return self.user, self.pass

def __init__(self, user, pass):
self.user = user
self.pass = pass

self.client = Client("connection string")
self.client.callback_login = get_login

... but obviously, the Client class, when it calls the callback,
doesn't pass a reference to the "self" object. How do I do this?

Do self.get_login. The difference is that this creates a so-called
"bound method". Google for that, and play around in the interpreter with
an object and references to it's methods, either through the class or
the instance to see the difference.

Diez

[Gary Herron]

catsclaw wrote:

I can't for the life of me figure out how to set a callback in
Python. I have a class, which wraps another class. The second class
needs a callback assigned. I don't want to use globals for it.
Here's what I'd like to do:

class MyWrapper:
def get_login(self, username):
return self.user, self.pass

def __init__(self, user, pass):
self.user = user
self.pass = pass

self.client = Client("connection string")
self.client.callback_login = get_login

Make that list line:

self.client.callback_login = self.get_login
Then you are passing a "bound" method (meaning bound to a particular instance).
The client class calls its callback_login as a normal function with parameters,
and the Wrapper get_login will be called on the proper instance of MyWrapper.

This is a very common thing for many uses, including callbacks.
Hoping I understood what you wanted correctly,
Gary Herron

... but obviously, the Client class, when it calls the callback,
doesn't pass a reference to the "self" object. How do I do this?

-- Chris
--
http://mail.python.org/mailman/listinfo/python-list