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<title>4.11 stringprep -- Internet String Preparation</title>
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<H1><A NAME="SECTION0061100000000000000000">
4.11 <tt class="module">stringprep</tt> --
         Internet String Preparation</A>
</H1>

<P>
<A NAME="module-stringprep"></A>

<P>
When identifying things (such as host names) in the internet, it is
often necessary to compare such identifications for
``equality''. Exactly how this comparison is executed may depend on
the application domain, e.g. whether it should be case-insensitive or
not. It may be also necessary to restrict the possible
identifications, to allow only identifications consisting of
``printable'' characters.

<P>
<a class="rfc" id='rfcref-87139' xml:id='rfcref-87139'
href="http://www.faqs.org/rfcs/rfc3454.html">RFC 3454</a> defines a procedure for ``preparing'' Unicode strings in
internet protocols. Before passing strings onto the wire, they are
processed with the preparation procedure, after which they have a
certain normalized form. The RFC defines a set of tables, which can be
combined into profiles. Each profile must define which tables it uses,
and what other optional parts of the <code>stringprep</code> procedure are
part of the profile. One example of a <code>stringprep</code> profile is
<code>nameprep</code>, which is used for internationalized domain names.

<P>
The module <tt class="module">stringprep</tt> only exposes the tables from RFC
3454. As these tables would be very large to represent them as
dictionaries or lists, the module uses the Unicode character database
internally. The module source code itself was generated using the
<code>mkstringprep.py</code> utility.

<P>
As a result, these tables are exposed as functions, not as data
structures. There are two kinds of tables in the RFC: sets and
mappings. For a set, <tt class="module">stringprep</tt> provides the ``characteristic
function'', i.e. a function that returns true if the parameter is part
of the set. For mappings, it provides the mapping function: given the
key, it returns the associated value. Below is a list of all functions
available in the module.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1039' xml:id='l2h-1039' class="function">in_table_a1</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableA.1 (Unassigned code points
in Unicode 3.2).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1040' xml:id='l2h-1040' class="function">in_table_b1</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableB.1 (Commonly mapped to
nothing).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1041' xml:id='l2h-1041' class="function">map_table_b2</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Return the mapped value for <var>code</var> according to tableB.2
(Mapping for case-folding used with NFKC).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1042' xml:id='l2h-1042' class="function">map_table_b3</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Return the mapped value for <var>code</var> according to tableB.3
(Mapping for case-folding used with no normalization).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1043' xml:id='l2h-1043' class="function">in_table_c11</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.1.1
(ASCII space characters).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1044' xml:id='l2h-1044' class="function">in_table_c12</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.1.2
(Non-ASCII space characters).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1045' xml:id='l2h-1045' class="function">in_table_c11_c12</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.1
(Space characters, union of C.1.1 and C.1.2).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1046' xml:id='l2h-1046' class="function">in_table_c21</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.2.1
(ASCII control characters).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1047' xml:id='l2h-1047' class="function">in_table_c22</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.2.2
(Non-ASCII control characters).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1048' xml:id='l2h-1048' class="function">in_table_c21_c22</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.2
(Control characters, union of C.2.1 and C.2.2).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1049' xml:id='l2h-1049' class="function">in_table_c3</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.3
(Private use).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1050' xml:id='l2h-1050' class="function">in_table_c4</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.4
(Non-character code points).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1051' xml:id='l2h-1051' class="function">in_table_c5</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.5
(Surrogate codes).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1052' xml:id='l2h-1052' class="function">in_table_c6</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.6
(Inappropriate for plain text).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1053' xml:id='l2h-1053' class="function">in_table_c7</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.7
(Inappropriate for canonical representation).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1054' xml:id='l2h-1054' class="function">in_table_c8</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.8
(Change display properties or are deprecated).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1055' xml:id='l2h-1055' class="function">in_table_c9</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableC.9
(Tagging characters).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1056' xml:id='l2h-1056' class="function">in_table_d1</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableD.1
(Characters with bidirectional property ``R'' or ``AL'').
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1057' xml:id='l2h-1057' class="function">in_table_d2</tt></b>(</nobr></td>
  <td><var>code</var>)</td></tr></table></dt>
<dd>
Determine whether <var>code</var> is in tableD.2
(Characters with bidirectional property ``L'').
</dl>

<P>

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