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| 55 | <H3><A NAME="SECTION0082111000000000000000"></A><A NAME="optparse-terminology"></A> |
| 56 | <BR> |
| 57 | 6.21.1.1 Terminology |
| 58 | </H3> |
| 59 | <DL> |
| 60 | <DT><STRONG>argument</STRONG></DT> |
| 61 | <DD>a string entered on the command-line, and passed by the shell to |
| 62 | <code>execl()</code> or <code>execv()</code>. In Python, arguments are elements of |
| 63 | <code>sys.argv[1:]</code> (<code>sys.argv[0]</code> is the name of the program being |
| 64 | executed). <span class="Unix">Unix</span> shells also use the term ``word''. |
| 65 | |
| 66 | <P> |
| 67 | It is occasionally desirable to substitute an argument list other |
| 68 | than <code>sys.argv[1:]</code>, so you should read ``argument'' as ``an element of |
| 69 | <code>sys.argv[1:]</code>, or of some other list provided as a substitute for |
| 70 | <code>sys.argv[1:]</code>''. |
| 71 | </DD> |
| 72 | <DT><STRONG>option </STRONG></DT> |
| 73 | <DD>an argument used to supply extra information to guide or customize the |
| 74 | execution of a program. There are many different syntaxes for |
| 75 | options; the traditional <span class="Unix">Unix</span> syntax is a hyphen (``-'') followed by a |
| 76 | single letter, e.g. <code>"-x"</code> or <code>"-F"</code>. Also, traditional <span class="Unix">Unix</span> |
| 77 | syntax allows multiple options to be merged into a single argument, |
| 78 | e.g. <code>"-x -F"</code> is equivalent to <code>"-xF"</code>. The GNU project |
| 79 | introduced <code>"-"</code> followed by a series of hyphen-separated words, |
| 80 | e.g. <code>"-file"</code> or <code>"-dry-run"</code>. These are the only two option |
| 81 | syntaxes provided by <tt class="module">optparse</tt>. |
| 82 | |
| 83 | <P> |
| 84 | Some other option syntaxes that the world has seen include: |
| 85 | |
| 86 | <UL> |
| 87 | <LI> |
| 88 | a hyphen followed by a few letters, e.g. <code>"-pf"</code> (this is |
| 89 | <em>not</em> the same as multiple options merged into a single argument) |
| 90 | |
| 91 | <P> |
| 92 | </LI> |
| 93 | <LI> |
| 94 | a hyphen followed by a whole word, e.g. <code>"-file"</code> (this is |
| 95 | technically equivalent to the previous syntax, but they aren't |
| 96 | usually seen in the same program) |
| 97 | |
| 98 | <P> |
| 99 | </LI> |
| 100 | <LI> |
| 101 | a plus sign followed by a single letter, or a few letters, |
| 102 | or a word, e.g. <code>"+f"</code>, <code>"+rgb"</code> |
| 103 | |
| 104 | <P> |
| 105 | </LI> |
| 106 | <LI> |
| 107 | a slash followed by a letter, or a few letters, or a word, e.g. |
| 108 | <code>"/f"</code>, <code>"/file"</code> |
| 109 | |
| 110 | <P> |
| 111 | </LI> |
| 112 | </UL> |
| 113 | |
| 114 | <P> |
| 115 | These option syntaxes are not supported by <tt class="module">optparse</tt>, and they never will |
| 116 | be. This is deliberate: the first three are non-standard on any |
| 117 | environment, and the last only makes sense if you're exclusively |
| 118 | targeting VMS, MS-DOS, and/or Windows. |
| 119 | </DD> |
| 120 | <DT><STRONG>option argument</STRONG></DT> |
| 121 | <DD>an argument that follows an option, is closely associated with that |
| 122 | option, and is consumed from the argument list when that option is. |
| 123 | With <tt class="module">optparse</tt>, option arguments may either be in a separate argument |
| 124 | from their option: |
| 125 | <div class="verbatim"><pre> |
| 126 | -f foo |
| 127 | --file foo |
| 128 | </pre></div> |
| 129 | |
| 130 | <P> |
| 131 | or included in the same argument: |
| 132 | <div class="verbatim"><pre> |
| 133 | -ffoo |
| 134 | --file=foo |
| 135 | </pre></div> |
| 136 | |
| 137 | <P> |
| 138 | Typically, a given option either takes an argument or it doesn't. |
| 139 | Lots of people want an ``optional option arguments'' feature, meaning |
| 140 | that some options will take an argument if they see it, and won't if |
| 141 | they don't. This is somewhat controversial, because it makes parsing |
| 142 | ambiguous: if <code>"-a"</code> takes an optional argument and <code>"-b"</code> is |
| 143 | another option entirely, how do we interpret <code>"-ab"</code>? Because of |
| 144 | this ambiguity, <tt class="module">optparse</tt> does not support this feature. |
| 145 | </DD> |
| 146 | <DT><STRONG>positional argument</STRONG></DT> |
| 147 | <DD>something leftover in the argument list after options have been |
| 148 | parsed, i.e. after options and their arguments have been parsed and |
| 149 | removed from the argument list. |
| 150 | </DD> |
| 151 | <DT><STRONG>required option</STRONG></DT> |
| 152 | <DD>an option that must be supplied on the command-line; note that the |
| 153 | phrase ``required option'' is self-contradictory in English. <tt class="module">optparse</tt> |
| 154 | doesn't prevent you from implementing required options, but doesn't |
| 155 | give you much help at it either. See <code>examples/required_1.py</code> and |
| 156 | <code>examples/required_2.py</code> in the <tt class="module">optparse</tt> source distribution for two |
| 157 | ways to implement required options with <tt class="module">optparse</tt>. |
| 158 | </DD> |
| 159 | </DL> |
| 160 | |
| 161 | <P> |
| 162 | For example, consider this hypothetical command-line: |
| 163 | <div class="verbatim"><pre> |
| 164 | prog -v --report /tmp/report.txt foo bar |
| 165 | </pre></div> |
| 166 | |
| 167 | <P> |
| 168 | <code>"-v"</code> and <code>"-report"</code> are both options. Assuming that |
| 169 | <b class="programopt">--report</b> takes one argument, <code>"/tmp/report.txt"</code> is an option |
| 170 | argument. <code>"foo"</code> and <code>"bar"</code> are positional arguments. |
| 171 | |
| 172 | <P> |
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