Object-Oriented Programming With Python (part 2) - Chaos And Destruction

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In Python, an object is automatically destroyed once the references to it are no longer in use, or when the Python script completes execution. A destructor is a special function which allows you to execute commands immediately prior to the destruction of an object.

You do not usually need to define a destructor - but if you want to see what it looks like, take a look at this:

class veryBigSnake:
# constructor
# now accepts name and type as arguments
def __init__(self, name="Peter Python", type="python"):
self.name = name
self.type = type
print "New snake in da house!"
# function to set snake name
def set_snake_name(self, name):
self.name = name
# function to set snake type
def set_snake_type(self, type):
self.type = type
# function to display name and type
def who_am_i(self):
print "My name is " + self.name + ", I'm a " + self.type + " and I'm
perfect for you! Take me home today!"
# destructor
def __del__(self):
print "Just killed the snake named " + self.name  + "!"

Note that a destructor must always be called __del__()

Here's a demonstration of how to use it:

>>> alpha = veryBigSnake("Bobby Boa", "boa constrictor")
New snake in da house!
>>> beta = veryBigSnake("Alan Adder", "harmless green adder")
New snake in da house!
>>> del beta
Just killed the snake named Alan Adder!
>>> del alpha
Just killed the snake named Bobby Boa!
>>>

And with multiple murder on my hands, it's now time to bid you goodbye. If you're interested in the more arcane aspects of Python's OO capabilities - operator overloading, private and public variables, and so on - you should consider visiting the following sites:

The official Python tutorial, at http://www.python.org/doc/current/tut/node11.html

The Python Cookbook, at http://aspn.activestate.com/ASPN/Cookbook/Python

The Vaults of Parnassus, at http://www.vex.net/parnassus/

Python HOWTOs, at http://py-howto.sourceforge.net/

The Python FAQ, at http://www.python.org/doc/FAQ.html

Until next time...stay healthy!

Note: All examples in this article have been tested on Linux/i586 with Python 1.5.2. Examples are illustrative only, and are not meant for a production environment. YMMV!\n

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