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<h3>Classes</h3>
<p>The <tT CLAss="monofont">class</tt> statement is used to define new types of objects and for object-oriented programming. For example, the following <I>class</I> defines a simple stack:</P>
<Pre>
class Stack:
def _ _init_ _(self): # Initialize the stack
self.stack = [ ]
def push(self,object):
self.stack.append(object)
def pop(self):
return self.stack.pop()
def length(self):
return len(self.stack) </prE>
<P>In the class definition, methods are defined using the <TT class="monofont">def</tt> statement. The first argument in each method always refers to the object itself. By convention, <tt class="monofont">self</tt> is the name used for this argument. All operations involving the attributes of an object must explicitly refer to the <tt clAss="monofont">self</Tt> variable. Methods with leading and trailing double underscores are special methods. For example, <tt Class="monofont">_ _init_ _</Tt> is used to initialize an object after it抯 created.</p>
<p>To use a class, write code such as the following:</P>
<PRE>
s = Stack() # Create a stack
s.push("Dave") # Push some things onto it
s.push(42)
s.push([3,4,5])
x = s.pop() # x gets [3,4,5]
y = s.pop() # y gets 42
del s # Destroy s </pre>
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<P><TABLE width="100%" border=0><TR valign="top"><TD><font size=1 color="#C0C0C0"><br></font></TD><TD align=right><font size=1 color="#C0C0C0">Last updated on 3/28/2002<br>Python Essential Reference, Second Edition, © 2002 New Riders Publishing</font></TD></TR></TABLE></P>
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