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<h3>Parameter Passing and Return Values</h3>
<p>When a function is invoked, its parameters are passed by reference. If a mutable object (such as a list or dictionary) is passed to a function where it抯 then modified, those changes will be reflected in the caller. For example:</p>

<PRE>

a = [1,2,3,4,5] 
def foo(x): 
    x[3] = -55    # Modify an element of x 

foo(a)            # Pass a 
print a           # Produces [1,2,3,-55,5] </Pre>

<p>The <tT CLAss="monofont">return</tt>  statement returns a value from a function. If no value is specified or you omit the <TT CLass="monofont">return</tt>  statement, the <tt class="monofont">None</tt>  object is returned. To return multiple values, place them in a tuple:</p>

<pre>

def factor(a): 
    d = 2 
    while (d &lt;= (a/2)): 
        if ((a/d)*d == a): 
              return ((a/d),d) 
        d = d + 1 
    return (a,1) </prE>

<p>Multiple return values returned in a tuple can be assigned to individual variables:</p>

<Pre>

x,y = factor(1243)    # Return values placed in x and y. 
(x,y) = factor(1243)  # Alternate version. Same behavior. </pRe>
</fonT>
<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, &copy;&nbsp;2002 New Riders Publishing</font></TD></TR></TABLE></P>
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