为什么这个python只捕获一个数字？

Question

我试图使用Python RE模块捕获字符串的具体数字好像'03'在' video [720P] [DHR] _sp03.mp4 '.

令我困惑的是:

当我使用'.*\D+(\d+).*mp4'它时,它成功捕获了两个数字03,但是当我使用时'.*\D*(\d+).*mp4',它只捕获了后面的数字3.

我知道python使用贪婪模式作为默认模式,这意味着尝试匹配尽可能多的文本.考虑到这一点,我想*和+后\D应相同则表现.那我在哪里错了？是什么导致了这种差异？谁能帮忙解释一下呢？

BTW:我使用python的在线正则表达式测试器:https://regex101.com/#python

Answer 1

差异的原因不是\D+第一个.*

现在正则表达式.*是贪婪的,并尝试尽可能多地匹配字符

所以当你写作

.*\D*(\d+).*mp4

该.*会匹配尽可能多的,因为它可以.那就是如果我们试图将其分解,那就像是

video [720P] [DHR] _sp03.mp4
|
.*

video [720P] [DHR] _sp03.mp4
 |
 .*
.....

video [720P] [DHR] _sp03.mp4
                      |
                      .* That is 0 is also matched by the .

video [720P] [DHR] _sp03.mp4
                      |
                      \D* Since the quantfier is zero or more, it matches nothing here without advancing to 3

video [720P] [DHR] _sp03.mp4
                       |
                      (\d+)

video [720P] [DHR] _sp03.mp4
                        |
                        .*

video [720P] [DHR] _sp03.mp4
                          |
                         mp4

现在当我们使用时\D+,匹配会稍微改变,因为正则数据引擎将被强制匹配数字(\D+)之前至少1个非数字((\d+)).这将消耗p数字之前的最后一位非数字

那是

.*将尝试尽可能多地匹配p,以便\D+能够匹配至少一个非数字,这将是p并且\d+将匹配您的03部分

video [720P] [DHR] _sp03.mp4
|
.*

video [720P] [DHR] _sp03.mp4
 |
 .*
.....

video [720P] [DHR] _sp03.mp4
                     |
                     \D+ The first non digit. Forced to match at least once.

video [720P] [DHR] _sp03.mp4
                      |
                      (\d+) 

video [720P] [DHR] _sp03.mp4
                       |
                      (\d+)

video [720P] [DHR] _sp03.mp4
                        |
                        .*

video [720P] [DHR] _sp03.mp4
                          |
                         mp4