Python URL 匹配(正则表达式) [英] Python URL matching (Regex)

问题描述

我已经尝试匹配以下 URL 几个小时，但似乎无法弄清楚，我很确定这并不难:

I've tried to match a the below URL for a couple of hours and can't seem to figure it out and Im quite sure its not that difficult:

网址可以是:

/course/lesson-one/

也可以是:

/course/lesson-one/chapter-one/

我所拥有的是与第二个 URL 匹配的以下内容:

What I have is the following which matches the second URL:

/course/([a-zA-Z]+[-a-zA-Z]*)/([a-zA-Z]+[-a-zA-Z]*)/

我想要的是第二部分是可选的，但我无法弄清楚我得到的最接近的是以下内容:

What I want is for the second part to be optional but I can't figure it out the closest I got was the following:

/course/([a-zA-Z]+[-a-zA-Z]*)/*([a-zA-Z]+[-a-zA-Z]*)/

但是上面出于某种原因遗漏了单词的最后一个字母，例如，如果 URL 是

But the above for some reason leaves out the last letter of the word for example if the URL is

/course/computers/

我最终得到字符串 'computer'

I end up with the string 'computer'

推荐答案

如果需要可选部件，您使用 ?.

You use ? if you need optional parts.

/course/([a-zA-Z][-a-zA-Z]*)/([a-zA-Z][-a-zA-Z]*/)?
#                                                 ^

(注意 [a-zA-Z]+[-a-zA-Z]* 等价于 [a-zA-Z][-a-zA-Z]*.)

(Note that [a-zA-Z]+[-a-zA-Z]* is equivalent to [a-zA-Z][-a-zA-Z]*.)

使用额外的分组 (?:...) 从匹配中排除 /，同时允许多个元素同时可选:

Use an additional grouping (?:…) to exclude the / from the match, while allowing multiple elements to be optional at once:

/course/([a-zA-Z][-a-zA-Z]*)/(?:([a-zA-Z][-a-zA-Z]*)/)?
#                            ~~~                     ~^

<小时>

您的第二个正则表达式吞下了最后一个字符，因为:

---

Your 2nd regex swallows the last character, because:

  /course/([a-zA-Z]+[-a-zA-Z]*)/*([a-zA-Z]+[-a-zA-Z]*)/
          ^^^^^^^^^^^^^^^^^^^^^  ~~~~~~~~~~~~~~~~~~~~~
        this matches 'computer'  and this matches the 's'.

由于 +，这个正则表达式中的第二组需要匹配一些长度为 1 或更多的字母，所以 's' 必须属于那里.

The second group in this regex required to match some alphabets with length 1 or more due to the +, so the 's' must belong there.

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