使用正则表达式捕获组（Python）

Kind of a noob here, apologies if I misstep.

这里有一个菜鸟,如果我错过了道歉。

I'm learning regular expressions and am on this lesson: https://regexone.com/lesson/capturing_groups.

我正在学习正则表达式并参与本课程:https://regexone.com/lesson/capturing_groups。

In the python interpreter, I try to use the parentheses to only capture what precedes the .pdf part of the search string but my result captures it despite using the parens. What am I doing wrong?

在python解释器中,我尝试使用括号仅捕获搜索字符串的.pdf部分之前的内容,但我的结果尽管使用了parens但仍然捕获了它。我究竟做错了什么?

import re
string_one = 'file_record_transcript.pdf'
string_two = 'file_07241999.pdf'
string_three = 'testfile_fake.pdf.tmp'

pattern = '^(file.+)\.pdf$'
a = re.search(pattern, string_one)
b = re.search(pattern, string_two)
c = re.search(pattern, string_three)

print(a.group() if a is not None else 'Not found')
print(b.group() if b is not None else 'Not found')
print(c.group() if c is not None else 'Not found')

Returns

file_record_transcript.pdf
file_07241999.pdf
Not found

But should return

但是应该回来

file_record_transcript
file_07241999
Not found

Thanks!

1 个解决方案

#1

You need the first captured group:

您需要第一个捕获的组:

a.group(1)
b.group(1)
...

without any captured group specification as argument to group(), it will show the full match, like what you're getting now.

没有任何捕获的组规范作为group()的参数,它将显示完全匹配,就像你现在得到的那样。

Here's an example:

这是一个例子:

In [8]: string_one = 'file_record_transcript.pdf'

In [9]: re.search(r'^(file.*)\.pdf$', string_one).group()
Out[9]: 'file_record_transcript.pdf'

In [10]: re.search(r'^(file.*)\.pdf$', string_one).group(1)
Out[10]: 'file_record_transcript'

#1