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In case it wasn't clear, options should be <i>optional</i>. A program should be able to run just fine with no options whatsoever. (Pick a random program from the <font style="font-variant: small-caps;">Unix</font> or GNU toolsets. Can it run without any options at all and still make sense? The only exceptions I can think of are <b class="program">find</b>, <b class="program">tar</b>, and <b class="program">dd</b>--all of which are mutant oddballs that have been rightly criticized for their non-standard syntax and confusing interfaces.) <P> Lots of people want their programs to have ``required options''. Think about it. If it's required, then it's <i>not optional</i>! If there is a piece of information that your program absolutely requires in order to run successfully, that's what positional arguments are for. (However, if you insist on adding ``required options'' to your programs, look in ``Extending Examples'' (section <A href="optparse-extending-examples.html#optparse-extending-examples">6.20.5</A>) for two ways of implementing them with <tt class="module">optparse</tt>.) <P> Consider the humble <b class="program">cp</b> utility, for copying files. It doesn't make much sense to try to copy files without supplying a destination and at least one source. Hence, <b class="program">cp</b> fails if you run it with no arguments. However, it has a flexible, useful syntax that does not rely on options at all: <P> <div class="verbatim"><pre> $ cp SOURCE DEST $ cp SOURCE ... DEST-DIR </pre></div> <P> You can get pretty far with just that. Most <b class="program">cp</b> implementations provide a bunch of options to tweak exactly how the files are copied: you can preserve mode and modification time, avoid following symlinks, ask before clobbering existing files, etc. But none of this distracts from the core mission of <b class="program">cp</b>, which is to copy one file to another, or N files to another directory. <P> <DIV CLASS="navigation"> <div class='online-navigation'><hr /> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="6.20.1.1 Terminology" rel="prev" title="6.20.1.1 Terminology" href="optparse-terminology.html"><img src='../icons/previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="6.20.1 Philosophy" rel="parent" title="6.20.1 Philosophy" href="optparse-philosophy.html"><img src='../icons/up.png' border='0' height='32' alt='Up One Level' width='32' /></A></td> <td class='online-navigation'><a rel="next" title="6.20.1.3 What are positional" rel="next" title="6.20.1.3 What are positional" href="optparse-positional-arguments.html"><img src='../icons/next.png' border='0' height='32' alt='Next Page' width='32' /></A></td> <td align="center" width="100%">Python Library Reference</td> <td class='online-navigation'><a rel="contents" title="Table of Contents" rel="contents" title="Table of Contents" href="contents.html"><img src='../icons/contents.png' border='0' height='32' alt='Contents' width='32' /></A></td> <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' border='0' height='32' alt='Module Index' width='32' /></a></td> <td class='online-navigation'><a rel="index" title="Index" rel="index" title="Index" href="genindex.html"><img src='../icons/index.png' border='0' height='32' alt='Index' width='32' /></A></td> </tr></table> <div class='online-navigation'> <b class="navlabel">Previous:</b> <a class="sectref" rel="prev" href="optparse-terminology.html">6.20.1.1 Terminology</A> <b class="navlabel">Up:</b> <a class="sectref" rel="parent" href="optparse-philosophy.html">6.20.1 Philosophy</A> <b class="navlabel">Next:</b> <a class="sectref" rel="next" href="optparse-positional-arguments.html">6.20.1.3 What are positional</A> </div> </div> <hr /> <span class="release-info">Release 2.3.4, documentation updated on May 20, 2004.</span> </DIV> <!--End of Navigation Panel--> <ADDRESS> See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. </ADDRESS> </BODY> </HTML>
