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<h3>
Generating an Executable Python Bytecode</h3>
<p>When loading a module, the Python interpreter first tries to load a byte-compiled version of the module (a <tT CLAss="monofont">.pyc</tt> or <TT CLass="monofont">.pyo</tT> bytecode file) from the system. If it doesn't find one, it automatically byte-compiles the module, and in case the permissions given to the user who is executing the command allow, a byte-compiled version of the module is saved in the disk for a later user. Note that it is a good idea to bytecompile all files before giving Python access to users who cannot save in that source directory. Otherwise, the interpreter has to byte-compile the module every time the module is loaded, which can slow down program startup considerably.</P>
<P>Even though a Python bytecode file can automatically be created when importing a module, you can manually create them whenever you need, as well. In order to explicitly byte-compile a source file (<Tt class="monofont">.py</tt>) to a <tt class="monofont">.pyc</tt> (or <tt cLasS="monofont">.pyo</tt>) bytecode file, you just need to execute the following code:</p>
<Pre>
import py_compile
pycompile.compile("anyfilename.py")
</prE>
<p>As you can see, the <a nAME="idx1073750157"></A>
<a namE="idx1073750158"></A>
<TT clasS="monofont">py_compile</TT> module provides a function called <A name="idx1073750159"></A>
<A NAme="idx1073750160"></a>
<tt class="monofont">compile()</tt> that does all the jobs. The general <a name="idx1073750161"></a>syntax for this function is</p>
<pRe>
compile(file [, cfile] [, dfile])
</pRe>
<p>where,</p>
<P><tablE borDER="1" CellsPACIng="0" ceLLPAddinG="1" WIDth="100%">
<colgroup align="left" span="2">
<tR vaLign="top">
<Td>
<fonT sizE="2">
<TT Class="monofont">file</TT>
</FOnt></td>
<TD>
<FOnt siZE="2">source filename</FOnt></td>
</tr>
<tr valign="top">
<td>
<font SizE="2">
<tt cLass="monofont">cfile</tT>
</fonT></TD>
<Td>
<fonT SIZe="2">target filename; defaults to source with <tt cLASS="monofont">c</tt> or <tt CLASs="monofont">o</tt> appended (<tt class="monofont">c</tt> normally and <tt class="monofont">o</tT> in optimizing mode, giving <tt ClasS="monofont">.pyc</tt> or <tt ClasS="monofont">.pyo</TT>)</Font></tD>
</TR>
<Tr valIGN="top">
<Td>
<fonT SIZe="2">
<tt class="monofont">dfile</tt>
</font></td>
<td>
<foNt sIze="2">filename to store error messages (defaults to source) <a Name="idx1073750162"></a>
<A namE="idx1073750163"></A>
<A Name="idx1073750164"></a>
<A NAMe="idx1073750165"></a>
<a nAME="idx1073750166"></A>
</font></TD>
</TR>
</colgroup>
</table></p>
<p>The <a name="idx1073750167"></A>
<a nAme="idx1073750168"></a>
<Tt claSs="monofont">compileall</tt> module can be used either as a script or as a module. It uses the <TT CLass="monofont">py_compile</tT> module to byte-compile all installed files (or all files in selected directories).</P>
<P>The following example compiles all files from the current directory:</P>
<pre>
import compileall.py
compileall.compile_dir(".", force=1)
</pRE>
<P>You can also use this module as a script, passing arguments to it. The <A name="idx1073750169"></A>
<A NAme="idx1073750170"></a>
<a name="idx1073750171"></a>syntax for usage as a script is as follows:</p>
<pre>
python compileall [-l] [-f] [-d destdir] [directory ...]
</pre>
<p>where,</p>
<p><tAblE borDer="1" ceLlspACINg="0" celLPADding="1" WIDTh="100%">
<colGROUp align="left" span="2">
<tr valign="top">
<td>
<FonT sizE="2">
<tt clAss="monofont">-l</tT>
</FONt></td>
<tD>
<FONt sizE="2">avoids recursing into directories</FONt></td>
</tR>
<TR Valign="top">
<td>
<font size="2">
<tt claSs="monofont">-f</tT>
</fonT></td>
<td>
<Font SIZE="2">forces rebuild even if timestamps are up-to-date</font></TD>
</TR>
<tr vaLIGN="top">
<td>
<foNT SIze="2">
<tt class="monofont">-d destdir</tt>
</font></td>
<td>
<fOnt Size="2">directory to store the error messages</Font></tD>
</tr>
</cOLGRoup>
</tABLE></p>
<p>The script reads the directories that are informed as arguments and compiles all the files that it finds there. If no directory arguments are given, the routine uses the <a nAME="idx1073750172"></A>
<a namE="idx1073750173"></A>
<TT class="monofont">sys.path</tt> variable.</p>
<p>Note that the current version doesn't recur down into subdirectories of a package. Another implementation detail is that it only recurs into the maximum number of 10 levels. (This number is hard coded in the module's code.) Also note that to generate both <tt class="monofont">.pyc</tt> and <tt ClaSs="monofont">.pyo</tt> files, you will need to run Python twice梠nce without the <Tt claSs="monofont">-O</tt> flag and once with it.<A NAMe="idx1073750174"></a>
<a nAME="idx1073750175"></A>
<a namE="idx1073750176"></A>
</P>
</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 1/30/2002<br>Python Developer's Handbook, © 2002 Sams Publishing</font></TD></TR></TABLE></P>
<TABLE border=0 width="100%" cellspacing=0 cellpadding=0><TR><td align=left width="15%" class="headingsubbarbg"><a href="232.html" title="Python Scripts"><font size="1">< BACK</font></a></td><td align=center width="70%" class="headingsubbarbg"><font size="1"><a href="popanote.asp?pubui=oreilly&bookname=0672319942&snode=233" target="_blank" title="Make a public or private annnotation">Make Note</a> | <a href="233.html" title="Use a Safari bookmark to remember this section">Bookmark</a></font></td><td align=right width="15%" class="headingsubbarbg"><a href="234.html" title="Interpreter"><font size="1">CONTINUE ></font></a></td></TR></TABLE>
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<br><TABLE width=100% bgcolor=white border=0 cellspacing=0 cellpadding=5><TR><TD><H4 class=Title>Index terms contained in this section</H4>
<font size=2>
byetcode<BR>
executable<BR>
<a href="#idx1073750176">generating</a><BR>
<a href="#idx1073750159">compile() function</a> <a href="#idx1073750164">2nd</a><BR>
<a href="#idx1073750167">compileall module</a><BR>
executable bytecode<BR>
<a href="#idx1073750175">generating</a><BR>
functions<BR>
<a href="#idx1073750160">compile()</a> <a href="#idx1073750165">2nd</a><BR>
generating<BR>
<a href="#idx1073750174">executable bytecode</a><BR>
modules<BR>
<a href="#idx1073750168">compileall</a><BR>
<a href="#idx1073750158">py_compile</a> <a href="#idx1073750163">2nd</a><BR>
<a href="#idx1073750170">scripts as</a><BR>
<a href="#idx1073750157">py_compile module</a> <a href="#idx1073750162">2nd</a><BR>
scripts<BR>
<a href="#idx1073750171">modules as</a><BR>
syntax<BR>
<a href="#idx1073750161">compile() function</a> <a href="#idx1073750166">2nd</a><BR>
<a href="#idx1073750169">modules as scripts</a><BR>
<a href="#idx1073750172">sys.path variable</a><BR>
variables<BR>
<a href="#idx1073750173">sys.path</a><BR>
<BR>
</font></TD></TR></TABLE>
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