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| 55 | <H2><A NAME="SECTION006250000000000000000"></A><A NAME="match-objects"></A> |
| 56 | <BR> |
| 57 | 4.2.5 Match Objects |
| 58 | </H2> |
| 59 | |
| 60 | <P> |
| 61 | <tt class="class">MatchObject</tt> instances support the following methods and |
| 62 | attributes: |
| 63 | |
| 64 | <P> |
| 65 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 66 | <td><nobr><b><tt id='l2h-901' xml:id='l2h-901' class="method">expand</tt></b>(</nobr></td> |
| 67 | <td><var>template</var>)</td></tr></table></dt> |
| 68 | <dd> |
| 69 | Return the string obtained by doing backslash substitution on the |
| 70 | template string <var>template</var>, as done by the <tt class="method">sub()</tt> method. |
| 71 | Escapes such as "<tt class="samp">\n</tt>" are converted to the appropriate |
| 72 | characters, and numeric backreferences ("<tt class="samp">\1</tt>", "<tt class="samp">\2</tt>") and |
| 73 | named backreferences ("<tt class="samp">\g<1></tt>", "<tt class="samp">\g<name></tt>") are replaced |
| 74 | by the contents of the corresponding group. |
| 75 | </dl> |
| 76 | |
| 77 | <P> |
| 78 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 79 | <td><nobr><b><tt id='l2h-902' xml:id='l2h-902' class="method">group</tt></b>(</nobr></td> |
| 80 | <td><var></var><big>[</big><var>group1, ...</var><big>]</big><var></var>)</td></tr></table></dt> |
| 81 | <dd> |
| 82 | Returns one or more subgroups of the match. If there is a single |
| 83 | argument, the result is a single string; if there are |
| 84 | multiple arguments, the result is a tuple with one item per argument. |
| 85 | Without arguments, <var>group1</var> defaults to zero (the whole match |
| 86 | is returned). |
| 87 | If a <var>groupN</var> argument is zero, the corresponding return value is the |
| 88 | entire matching string; if it is in the inclusive range [1..99], it is |
| 89 | the string matching the corresponding parenthesized group. If a |
| 90 | group number is negative or larger than the number of groups defined |
| 91 | in the pattern, an <tt class="exception">IndexError</tt> exception is raised. |
| 92 | If a group is contained in a part of the pattern that did not match, |
| 93 | the corresponding result is <code>None</code>. If a group is contained in a |
| 94 | part of the pattern that matched multiple times, the last match is |
| 95 | returned. |
| 96 | |
| 97 | <P> |
| 98 | If the regular expression uses the <tt class="regexp">(?P<<var>name</var>>...)</tt> syntax, |
| 99 | the <var>groupN</var> arguments may also be strings identifying groups by |
| 100 | their group name. If a string argument is not used as a group name in |
| 101 | the pattern, an <tt class="exception">IndexError</tt> exception is raised. |
| 102 | |
| 103 | <P> |
| 104 | A moderately complicated example: |
| 105 | |
| 106 | <P> |
| 107 | <div class="verbatim"><pre> |
| 108 | m = re.match(r"(?P<int>\d+)\.(\d*)", '3.14') |
| 109 | </pre></div> |
| 110 | |
| 111 | <P> |
| 112 | After performing this match, <code>m.group(1)</code> is <code>'3'</code>, as is |
| 113 | <code>m.group('int')</code>, and <code>m.group(2)</code> is <code>'14'</code>. |
| 114 | </dl> |
| 115 | |
| 116 | <P> |
| 117 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 118 | <td><nobr><b><tt id='l2h-903' xml:id='l2h-903' class="method">groups</tt></b>(</nobr></td> |
| 119 | <td><var></var><big>[</big><var>default</var><big>]</big><var></var>)</td></tr></table></dt> |
| 120 | <dd> |
| 121 | Return a tuple containing all the subgroups of the match, from 1 up to |
| 122 | however many groups are in the pattern. The <var>default</var> argument is |
| 123 | used for groups that did not participate in the match; it defaults to |
| 124 | <code>None</code>. (Incompatibility note: in the original Python 1.5 |
| 125 | release, if the tuple was one element long, a string would be returned |
| 126 | instead. In later versions (from 1.5.1 on), a singleton tuple is |
| 127 | returned in such cases.) |
| 128 | </dl> |
| 129 | |
| 130 | <P> |
| 131 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 132 | <td><nobr><b><tt id='l2h-904' xml:id='l2h-904' class="method">groupdict</tt></b>(</nobr></td> |
| 133 | <td><var></var><big>[</big><var>default</var><big>]</big><var></var>)</td></tr></table></dt> |
| 134 | <dd> |
| 135 | Return a dictionary containing all the <em>named</em> subgroups of the |
| 136 | match, keyed by the subgroup name. The <var>default</var> argument is |
| 137 | used for groups that did not participate in the match; it defaults to |
| 138 | <code>None</code>. |
| 139 | </dl> |
| 140 | |
| 141 | <P> |
| 142 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 143 | <td><nobr><b><tt id='l2h-905' xml:id='l2h-905' class="method">start</tt></b>(</nobr></td> |
| 144 | <td><var></var><big>[</big><var>group</var><big>]</big><var></var>)</td></tr></table></dt> |
| 145 | <dd> |
| 146 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 147 | <td><nobr><b><tt id='l2h-906' xml:id='l2h-906' class="method">end</tt></b>(</nobr></td> |
| 148 | <td><var></var><big>[</big><var>group</var><big>]</big><var></var>)</td></tr></table></dt> |
| 149 | <dd>Return the indices of the start and end of the substring |
| 150 | matched by <var>group</var>; <var>group</var> defaults to zero (meaning the whole |
| 151 | matched substring). |
| 152 | Return <code>-1</code> if <var>group</var> exists but |
| 153 | did not contribute to the match. For a match object |
| 154 | <var>m</var>, and a group <var>g</var> that did contribute to the match, the |
| 155 | substring matched by group <var>g</var> (equivalent to |
| 156 | <code><var>m</var>.group(<var>g</var>)</code>) is |
| 157 | |
| 158 | <P> |
| 159 | <div class="verbatim"><pre> |
| 160 | m.string[m.start(g):m.end(g)] |
| 161 | </pre></div> |
| 162 | |
| 163 | <P> |
| 164 | Note that |
| 165 | <code>m.start(<var>group</var>)</code> will equal <code>m.end(<var>group</var>)</code> if |
| 166 | <var>group</var> matched a null string. For example, after <code><var>m</var> = |
| 167 | re.search('b(c?)', 'cba')</code>, <code><var>m</var>.start(0)</code> is 1, |
| 168 | <code><var>m</var>.end(0)</code> is 2, <code><var>m</var>.start(1)</code> and |
| 169 | <code><var>m</var>.end(1)</code> are both 2, and <code><var>m</var>.start(2)</code> raises |
| 170 | an <tt class="exception">IndexError</tt> exception. |
| 171 | </dl> |
| 172 | |
| 173 | <P> |
| 174 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 175 | <td><nobr><b><tt id='l2h-907' xml:id='l2h-907' class="method">span</tt></b>(</nobr></td> |
| 176 | <td><var></var><big>[</big><var>group</var><big>]</big><var></var>)</td></tr></table></dt> |
| 177 | <dd> |
| 178 | For <tt class="class">MatchObject</tt> <var>m</var>, return the 2-tuple |
| 179 | <code>(<var>m</var>.start(<var>group</var>), <var>m</var>.end(<var>group</var>))</code>. |
| 180 | Note that if <var>group</var> did not contribute to the match, this is |
| 181 | <code>(-1, -1)</code>. Again, <var>group</var> defaults to zero. |
| 182 | </dl> |
| 183 | |
| 184 | <P> |
| 185 | <dl><dt><b><tt id='l2h-908' xml:id='l2h-908' class="member">pos</tt></b></dt> |
| 186 | <dd> |
| 187 | The value of <var>pos</var> which was passed to the <tt class="function">search()</tt> or |
| 188 | <tt class="function">match()</tt> method of the <tt class="class">RegexObject</tt>. This is the |
| 189 | index into the string at which the RE engine started looking for a |
| 190 | match. |
| 191 | </dl> |
| 192 | |
| 193 | <P> |
| 194 | <dl><dt><b><tt id='l2h-909' xml:id='l2h-909' class="member">endpos</tt></b></dt> |
| 195 | <dd> |
| 196 | The value of <var>endpos</var> which was passed to the <tt class="function">search()</tt> |
| 197 | or <tt class="function">match()</tt> method of the <tt class="class">RegexObject</tt>. This is the |
| 198 | index into the string beyond which the RE engine will not go. |
| 199 | </dl> |
| 200 | |
| 201 | <P> |
| 202 | <dl><dt><b><tt id='l2h-910' xml:id='l2h-910' class="member">lastindex</tt></b></dt> |
| 203 | <dd> |
| 204 | The integer index of the last matched capturing group, or <code>None</code> |
| 205 | if no group was matched at all. For example, the expressions |
| 206 | <tt class="regexp">(a)b</tt>, <tt class="regexp">((a)(b))</tt>, and <tt class="regexp">((ab))</tt> will have |
| 207 | <code>lastindex == 1</code> if applied to the string <code>'ab'</code>, |
| 208 | while the expression <tt class="regexp">(a)(b)</tt> will have <code>lastindex == 2</code>, |
| 209 | if applied to the same string. |
| 210 | </dl> |
| 211 | |
| 212 | <P> |
| 213 | <dl><dt><b><tt id='l2h-911' xml:id='l2h-911' class="member">lastgroup</tt></b></dt> |
| 214 | <dd> |
| 215 | The name of the last matched capturing group, or <code>None</code> if the |
| 216 | group didn't have a name, or if no group was matched at all. |
| 217 | </dl> |
| 218 | |
| 219 | <P> |
| 220 | <dl><dt><b><tt id='l2h-912' xml:id='l2h-912' class="member">re</tt></b></dt> |
| 221 | <dd> |
| 222 | The regular expression object whose <tt class="method">match()</tt> or |
| 223 | <tt class="method">search()</tt> method produced this <tt class="class">MatchObject</tt> instance. |
| 224 | </dl> |
| 225 | |
| 226 | <P> |
| 227 | <dl><dt><b><tt id='l2h-913' xml:id='l2h-913' class="member">string</tt></b></dt> |
| 228 | <dd> |
| 229 | The string passed to <tt class="function">match()</tt> or <tt class="function">search()</tt>. |
| 230 | </dl> |
| 231 | |
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