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<H2><A NAME="SECTION006250000000000000000"><!--x--></A><A NAME="match-objects"><!--z--></A>
<BR>
4.2.5 Match Objects
</H2>
<P>
<tt class="class">MatchObject</tt> instances support the following methods and
attributes:
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-864' class="method">expand</tt></b>(</nobr></td>
<td><var>template</var>)</td></tr></table></dt>
<dd>
Return the string obtained by doing backslash substitution on the
template string <var>template</var>, as done by the <tt class="method">sub()</tt> method.
Escapes such as "<tt class="samp">\n</tt>" are converted to the appropriate
characters, and numeric backreferences ("<tt class="samp">\1</tt>", "<tt class="samp">\2</tt>") and
named backreferences ("<tt class="samp">\g<1></tt>", "<tt class="samp">\g<name></tt>") are replaced
by the contents of the corresponding group.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-865' class="method">group</tt></b>(</nobr></td>
<td><big>[</big><var>group1, ...</var><big>]</big>)</td></tr></table></dt>
<dd>
Returns one or more subgroups of the match. If there is a single
argument, the result is a single string; if there are
multiple arguments, the result is a tuple with one item per argument.
Without arguments, <var>group1</var> defaults to zero (the whole match
is returned).
If a <var>groupN</var> argument is zero, the corresponding return value is the
entire matching string; if it is in the inclusive range [1..99], it is
the string matching the corresponding parenthesized group. If a
group number is negative or larger than the number of groups defined
in the pattern, an <tt class="exception">IndexError</tt> exception is raised.
If a group is contained in a part of the pattern that did not match,
the corresponding result is <code>None</code>. If a group is contained in a
part of the pattern that matched multiple times, the last match is
returned.
<P>
If the regular expression uses the <tt class="regexp">(?P<<var>name</var>>...)</tt> syntax,
the <var>groupN</var> arguments may also be strings identifying groups by
their group name. If a string argument is not used as a group name in
the pattern, an <tt class="exception">IndexError</tt> exception is raised.
<P>
A moderately complicated example:
<P>
<div class="verbatim"><pre>
m = re.match(r"(?P<int>\d+)\.(\d*)", '3.14')
</pre></div>
<P>
After performing this match, <code>m.group(1)</code> is <code>'3'</code>, as is
<code>m.group('int')</code>, and <code>m.group(2)</code> is <code>'14'</code>.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-866' class="method">groups</tt></b>(</nobr></td>
<td><big>[</big><var>default</var><big>]</big>)</td></tr></table></dt>
<dd>
Return a tuple containing all the subgroups of the match, from 1 up to
however many groups are in the pattern. The <var>default</var> argument is
used for groups that did not participate in the match; it defaults to
<code>None</code>. (Incompatibility note: in the original Python 1.5
release, if the tuple was one element long, a string would be returned
instead. In later versions (from 1.5.1 on), a singleton tuple is
returned in such cases.)
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-867' class="method">groupdict</tt></b>(</nobr></td>
<td><big>[</big><var>default</var><big>]</big>)</td></tr></table></dt>
<dd>
Return a dictionary containing all the <i>named</i> subgroups of the
match, keyed by the subgroup name. The <var>default</var> argument is
used for groups that did not participate in the match; it defaults to
<code>None</code>.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-868' class="method">start</tt></b>(</nobr></td>
<td><big>[</big><var>group</var><big>]</big>)</td></tr></table></dt>
<dd>
<dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-869' class="method">end</tt></b>(</nobr></td>
<td><big>[</big><var>group</var><big>]</big>)</td></tr></table></dt>
<dd>Return the indices of the start and end of the substring
matched by <var>group</var>; <var>group</var> defaults to zero (meaning the whole
matched substring).
Return <code>-1</code> if <var>group</var> exists but
did not contribute to the match. For a match object
<var>m</var>, and a group <var>g</var> that did contribute to the match, the
substring matched by group <var>g</var> (equivalent to
<code><var>m</var>.group(<var>g</var>)</code>) is
<P>
<div class="verbatim"><pre>
m.string[m.start(g):m.end(g)]
</pre></div>
<P>
Note that
<code>m.start(<var>group</var>)</code> will equal <code>m.end(<var>group</var>)</code> if
<var>group</var> matched a null string. For example, after <code><var>m</var> =
re.search('b(c?)', 'cba')</code>, <code><var>m</var>.start(0)</code> is 1,
<code><var>m</var>.end(0)</code> is 2, <code><var>m</var>.start(1)</code> and
<code><var>m</var>.end(1)</code> are both 2, and <code><var>m</var>.start(2)</code> raises
an <tt class="exception">IndexError</tt> exception.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-870' class="method">span</tt></b>(</nobr></td>
<td><big>[</big><var>group</var><big>]</big>)</td></tr></table></dt>
<dd>
For <tt class="class">MatchObject</tt> <var>m</var>, return the 2-tuple
<code>(<var>m</var>.start(<var>group</var>), <var>m</var>.end(<var>group</var>))</code>.
Note that if <var>group</var> did not contribute to the match, this is
<code>(-1, -1)</code>. Again, <var>group</var> defaults to zero.
</dl>
<P>
<dl><dt><b><tt id='l2h-871' class="member">pos</tt></b></dt>
<dd>
The value of <var>pos</var> which was passed to the <tt class="function">search()</tt> or
<tt class="function">match()</tt> method of the <tt class="class">RegexObject</tt>. This is the
index into the string at which the RE engine started looking for a
match.
</dl>
<P>
<dl><dt><b><tt id='l2h-872' class="member">endpos</tt></b></dt>
<dd>
The value of <var>endpos</var> which was passed to the <tt class="function">search()</tt>
or <tt class="function">match()</tt> method of the <tt class="class">RegexObject</tt>. This is the
index into the string beyond which the RE engine will not go.
</dl>
<P>
<dl><dt><b><tt id='l2h-873' class="member">lastindex</tt></b></dt>
<dd>
The integer index of the last matched capturing group, or <code>None</code>
if no group was matched at all. For example, the expressions
<tt class="regexp">(a)b</tt>, <tt class="regexp">((a)(b))</tt>, and <tt class="regexp">((ab))</tt> will have
<code>lastindex == 1</code> if applyied to the string <code>'ab'</code>,
while the expression <tt class="regexp">(a)(b)</tt> will have <code>lastindex == 2</code>,
if applyied to the same string.
</dl>
<P>
<dl><dt><b><tt id='l2h-874' class="member">lastgroup</tt></b></dt>
<dd>
The name of the last matched capturing group, or <code>None</code> if the
group didn't have a name, or if no group was matched at all.
</dl>
<P>
<dl><dt><b><tt id='l2h-875' class="member">re</tt></b></dt>
<dd>
The regular expression object whose <tt class="method">match()</tt> or
<tt class="method">search()</tt> method produced this <tt class="class">MatchObject</tt> instance.
</dl>
<P>
<dl><dt><b><tt id='l2h-876' class="member">string</tt></b></dt>
<dd>
The string passed to <tt class="function">match()</tt> or <tt class="function">search()</tt>.
</dl>
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<span class="release-info">Release 2.3.4, documentation updated on May 20, 2004.</span>
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