如何从python中的正则表达式匹配返回字符串？
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How do I return a string from a regex match in python?
提问by Hyman Dalton
I am running through lines in a text file using a pythonscript.
I want to search for an imgtag within the text document and return the tag as text.
我正在使用python脚本运行文本文件中的行。我想img在文本文档中搜索标签并将标签作为文本返回。
When I run the regex re.match(line)it returns a _sre.SRE_MATCHobject.
How do I get it to return a string?
当我运行正则表达式时，re.match(line)它返回一个 _sre.SRE_MATCH对象。我如何让它返回一个字符串？
import sys
import string
import re
f = open("sample.txt", 'r' )
l = open('writetest.txt', 'w')
count = 1
for line in f:
line = line.rstrip()
imgtag = re.match(r'<img.*?>',line)
print("yo it's a {}".format(imgtag))
When run it prints:
运行时打印：
yo it's a None
yo it's a None
yo it's a None
yo it's a <_sre.SRE_Match object at 0x7fd4ea90e578>
yo it's a None
yo it's a <_sre.SRE_Match object at 0x7fd4ea90e578>
yo it's a None
yo it's a <_sre.SRE_Match object at 0x7fd4ea90e578>
yo it's a <_sre.SRE_Match object at 0x7fd4ea90e5e0>
yo it's a None
yo it's a None
采纳答案by wflynny
You should use re.MatchObject.group(0). Like
你应该使用re.MatchObject.group(0). 喜欢
imtag = re.match(r'<img.*?>', line).group(0)
Edit:
编辑：
You also might be better off doing something like
你也可能会更好地做类似的事情
imgtag = re.match(r'<img.*?>',line)
if imtag:
print("yo it's a {}".format(imgtag.group(0)))
to eliminate all the Nones.
消除所有的Nones。
回答by Explosion Pills
imgtag.group(0)or imgtag.group(). This returns the entire match as a string. You are not capturing anything else either.
imgtag.group(0)或imgtag.group()。这将整个匹配项作为字符串返回。你也没有捕捉任何其他东西。
回答by newtover
Considering there might be several imgtags I would recommend re.findall:
考虑到img我可能会推荐几个标签re.findall：
import re
with open("sample.txt", 'r') as f_in, open('writetest.txt', 'w') as f_out:
for line in f_in:
for img in re.findall('<img[^>]+>', line):
print >> f_out, "yo it's a {}".format(img)
回答by Sergii Shcherbak
Note that re.match(pattern, string, flags=0)only returns matches at the beginningof the string. If you want to locate a match anywherein the string, use re.search(pattern, string, flags=0)instead (https://docs.python.org/3/library/re.html). This will scan the string and return the first match object. Then you can extract the matching string with match_object.group(0)as the folks suggested.
请注意，re.match(pattern, string, flags=0)仅返回字符串开头的匹配项。如果要在字符串中的任何位置找到匹配项，请re.search(pattern, string, flags=0)改用 ( https://docs.python.org/3/library/re.html)。这将扫描字符串并返回第一个匹配对象。然后您可以match_object.group(0)按照人们的建议提取匹配的字符串。
