signals

I am trying to define a "before_save" method in certain classes in my django 1.2 project. I'm having trouble connecting the signal to the class method in models.py. class MyClass(models.Model): .... def before_save(self, sender, instance, *args, **kwargs): self.test_field = "It worked" I've tried putting pre_save.connect(before_save, sender='self') in 'MyClass' itself, but nothing happens. I've also tried putting it at the bottom of the models.py file: pre_save.connect(MyClass.before_save, sender=MyClass) I read about connecting signals to class methods here , but can't figure out the code.

I'm trying to rollback on an error, but still let the client receive the error . This might actually be impossible, unless there is a way to access the error in an exception handler. It's possible to "throw" from an exception, i.e. it's possible to raise a signal : CREATE PROCEDURE p () BEGIN DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN SIGNAL SQLSTATE VALUE '99999' SET MESSAGE_TEXT = 'An error occurred'; END; DROP TABLE no_such_table; END; But this sample code from the MySQL doc looks horrible , because it literally swallows all errors and jams them into one. SHOW ERRORS seems relevant, but I

Is there anyway I can make my script execute one of my functions when Ctrl+c is hit when the script is running? Take a look at signal handlers . CTRL-C corresponds to SIGINT (signal #2 on posix systems). Example: #!/usr/bin/env python import signal import sys def signal_handler(signal, frame): print 'You pressed Ctrl+C - or killed me with -2' sys.exit(0) signal.signal(signal.SIGINT, signal_handler) print 'Press Ctrl+C' signal.pause() Sure. try: # Your normal block of code except KeyboardInterrupt: # Your code which is executed when CTRL+C is pressed. finally: # Your code which is always

When my application crashes with a segmentation fault I'd like to get a core dump from the system. I do that by configuring before hand ulimit -c unlimited I would also like to have an indication in my application logs that a segmentation fault has occured. I do that by using sigaction() . If I do that however, the signal does not reach its default handling and a core dump is not saved. How can I have both the system core dump an a log line from my own signal handler at the same time? Overwrite the default signal handler for SIGSEGV to call your custom logging function. After it is logged,

I'm trying to build a python timeout exception that runs in milliseconds. The python signal.alarm function has a 1 second resolution. How would one get an equivalent function that requests a SIGALRM signal to a given process in, say milliseconds, as opposed to seconds? I've found no simple solutions as of yet. Thanks in advance for your input. Use signal.setitimer() instead. 来源： https://stackoverflow.com/questions/3770711/signal-alarm-function-with-resolution-greater-than-1-second

When we want to pass data to an event subscriber, we use EventArgs (or CustomEventArgs) for this. .Net provides a build in type EventHandler that uses as a parameter an instance of EventArgs class that is build in as well. What about cases, when I need to notify a subscriber that some action is over, for example search is over? I don't want to even use EventArgs, that won't contain anything. Is there a build in type for signaling another class, without the need to use empty EventArgs? Carsten You can do a couple of things: Use your normal event with EventHandler and the basic EventArg class -

I recently started to use signals in my Django project (v. 1.3) and they all work fine except that I just can't figure out why the m2m_changed signal never gets triggered on my model. The Section instance is edited by adding/deleting PageChild inline instances on an django admin form. I tried to register the callback function either way as described in the documentation, but don't get any result. Excerpt from my models.py from django.db import models from django.db.models.signals import m2m_changed class Section(models.Model): name = models.CharField(unique = True, max_length = 100) pages =