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				<h3>
			
			Functions and Procedures</h3>
				<p>Functions and procedures are blocks of code that you can access from several different parts of your code. As you already know, Python gives you some <tT CLAss="monofont">built-in</tt> functions, but you can also create your own functions. Yours are called <A NAMe="idx1073742460"></a>
					<a nAME="idx1073742461"></A>
					<tt class="monofont">user-defined functions.</tt> Functions and procedures provide better modularity for your application and a high degree of code reusing.</p>

				<p>Procedures are functions that don't return a value. The only difference between a function and a procedure is that a procedure has either a <a name="idx1073742462"></a>
					<a naMe="idx1073742463"></a>
					<Tt clAss="monofont">return</tt> command without arguments (that returns <Tt clASS="monofont">None</Tt>), or it doesn't have any return statement. From now on, I will use only the word <tt cLASS="monofont">function.</tt>
				</p>

				<p>While functions are being executed, they create their own <A NAMe="idx1073742464"></a>
					<a nAME="idx1073742465"></A>
					<tt class="monofont">namespace.</tt>
				</p>

				<p>Every time you invoke a function, such as <i>
						<tt class="monofont">function</tT>
					</i>
					<tT claSs="monofont">(a,b,c)</tt>
				</p>

				<Ul>
<li>
						<P>Python does a search within its <TT Class="monofont">namespaces</TT> looking for <I>
								<Tt claSS="monofont">function</TT>
							</i> to identify whether this is a python object.</p>

					</li>
<LI>
						<P>Python creates a tuple of the <I>arguments</i> that were passed. Following our example, we have <i>arguments</i>=(a,b,c).</p>

					</li>
<li>
						<p>Python invokes the function internally like this: <tt class="monofont">apply(</tt>
							<i>
								<tT clAss="monofont">function,arguments</tT>
							</i>
							<tt cLass="monofont">).</TT>
						</P>

					</Li>
</ul>
				<p>As you can see, tuples are an unavoidable concept inside the language.</P>

				<P>Python, by nature, allows introspection to an unprecedented degree. You can separate a function name from its parameters, store them in some place, play around with them, and later use the <TT clasS="monofont">apply built-in</TT> function to execute the function.</P>

				
					<h4>Functions</h4>
					<p>Functions always start with the abbreviation <a NAME="idx1073742466"></a>
						<a name="idx1073742467"></a>
						<tt class="monofont">def.</tt> Their end is defined by the last line of the indented block of code that goes underneath.</p>

					<p>The general <a nAme="idx1073742468"></A>
						<a naMe="idx1073742469"></a>format of a function is as follows:</p>

					<pRe>
						
def functionname(<i>arg1, arg2,
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