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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> | |
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