In addition to the signal mechanism, window system events can also be connected to callback functions. Window resizing, key press, scroll event etc. are some of common window system events. These events are reported to application”s main loop. From there, they are passed along via signals to the callback functions.

Some of the system events are listed below −

• button_press_event
• button_release_event
• scroll_event
• motion_notify_event
• delete_event
• destroy_event
• expose_event
• key_press_event
• key_release_event

The connect() method is used to associate the event with callback function following the syntax −

Object.connect(name, function, data)

Here, name stands for the string corresponding to the name of event which is to be captured. And, function is name of the callback function that is to be called when an event occurs. Data is the argument to be passed on to the callback function.

Hence, the following code connects a Button widget and captures the button_press event −

self.btn.connect("button_press_event", self.hello)

The following will be the Prototype of hello() function −

def hello(self,widget,event):

Example

The following is the code for button event handler −

import gtk
class PyApp(gtk.Window):
   def __init__(self):
      super(PyApp, self).__init__()
      self.set_title("Hello World in PyGTK")
      self.set_default_size(400,300)
      self.set_position(gtk.WIN_POS_CENTER)
		
      self.label = gtk.Label("Enter name")
      self.entry = gtk.Entry()
      self.btn = gtk.Button("Say Hello")
      self.btn.connect("button_press_event", self.hello)
		
      fixed = gtk.Fixed()
      fixed.put(self.label, 100,100)
      fixed.put(self.entry, 100,125)
      fixed.put(self.btn,100,150)
		
      self.add(fixed)
      self.show_all()
		
   def hello(self,widget,event):
      print "hello",self.entry.get_text()

PyApp()
gtk.main()

When you run the above code, it displays the following output on the console −

Hello TutorialsPoint