Python 正则表达式的 Match 对象的 group 方法

用法介绍

match.group([group1, ...])

返回 match 的一个或多个子组。

如果只有唯的一参数，返回单一的子符串；如果有多个参数，结果是对应每一个参数的元素组成的 tuple 。
如果没有参数， group1 的默认值为 0 （返回整个匹配的字符串）。

如果一个 groupN 参数的值为 0 ，对应的返回值为整个匹配的字符串；如果参数值在 1 到 99 之间（含），返回对应的括号组匹配的字符串。

如果组号参数 （groupN）为负数，或者大于定义在模式中的组的个数，会抛出一个 IndexError 异常。

如果模式中的某个组没有匹配（例如：(\w+ )?，(\w+ )*），对应的结果为 None 。

如果模式中的某个组匹配了多次（例如：(\w+ )+，(\w+ )*），将返回最后匹配的字符串。

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, group1 defaults to zero (the whole match is returned). If a groupN 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 IndexError exception is raised. If a group is contained in a part of the pattern that did not match, the corresponding result is None. If a group is contained in a part of the pattern that matched multiple times, the last match is returned.

示例

程序

# coding=utf-8

import re

s = "[this is a book]"
PATTERN = "\[(((\w+)(\s+)?)+)\]"

m = re.search(PATTERN, s, re.DOTALL)
if m:
    for i in range(5):
        print("m.group(%d) => '%s', start = %d, end = %d" % (i, m.group(i), m.start(i), m.end(i)))

    it = re.finditer("(\w+)(\s+)?", m.group(1))
    for match in it:
        print("m.group(1, 2) => '%s','%s'" % match.group(1, 2))

运行结果

m.group(0) => '[this is a book]', start = 0, end = 16
m.group(1) => 'this is a book', start = 1, end = 15
m.group(2) => 'book', start = 11, end = 15
m.group(3) => 'book', start = 11, end = 15
m.group(4) => ' ', start = 10, end = 11
m.group(1, 2) => 'this',' '
m.group(1, 2) => 'is',' '
m.group(1, 2) => 'a',' '
m.group(1, 2) => 'book','None'

参考

https://docs.python.org/3.6/library/re.html#re.match.group