How can I trigger and listen for events in python ?

Question

How can I trigger and listen for events in python ?

I need a practical example..

thanks

Update

#add Isosurface button
def addIso():
    #trigger event

self.addButton = tk.Button(self.leftFrame, text="Add", command=addIso) #.grid(column=3, row=1)
self.addButton.pack(in_=self.leftFrame, side="right", pady=2)

Answer 1

There's a bind function for TKinter objects that takes two parameters: the first is a string representing the name of the event you want to listen for (probably "" in this case), and the second is a method which takes the triggering event as a parameter.

Example:

def addButton_click(event):
    print 'button clicked'
self.addButton.bind("<Button-1>", addButton_click)

I believe this will still work even if used from another class:

class X:
    def addButton_click(self, event):
        print 'button clicked'
...
inst = X()
self.addButton.bind("<Button-1>", inst.addButton_click)

Answer 2

Something like this:

#add Isosurface button
def addIso(event):
    #trigger event

self.addButton = tk.Button(self.leftFrame, text="Add") #.grid(column=3, row=1)
self.addButton.pack(in_=self.leftFrame, side="right", pady=2)
self.addButton.bind("<Button-1>", addIso)

From: http://www.bembry.org/technology/python/notes/tkinter_3.php

Answer 3

If you are using IronPython with Windows Presentation Foundation (WPF), you can find pyevent.py in the Ironpython\Tutorial directory. This lets you write stuff like:

import clr
clr.AddReferenceByPartialName("PresentationFramework")
import System
import pyevent

class myclass(object):
    def __init__(self):
        self._PropertyChanged, self._OnPropertyChanged = pyevent.make_event()
        self.initialize()

    def add_PropertyChanged(self, handler):
        self._PropertyChanged += handler

    def remove_PropertyChanged(self, handler):
        self._PropertyChanged -= handler

    def raiseAPropertyChangedEvent(self, name):
        self._OnPropertyChanged(self, System.ComponentModel.PropertyChangedEventArgs(name))

Answer 4

Based on your comments to some of the existing answers, I think what you want is something like the pubsub module. In the context of Tkinter, events are single purpose -- one event fires on one widget, and some handler handles the event (though there could be multiple handlers involved).

What it sounds like you want is more of a broadcast model -- your widget says "hey, the user did something" and any other module can register interest and get notifications without knowing specifically what widget or low level event caused that to happen.

I use this in an app that supports plugins. Plugins can say something like "call my 'open' method when the user opens a new file". They don't care how the user does it (ie: whether it was from the File menu, or a toolbar icon or a shortcut), only that it happened.

In this case, you would configure your button to call a specific method, typically in the same module that creates the button. That method would then use the pubsub module to publish some generic sort of event that other modules listen for and respond to.