Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
256 views
in Technique[技术] by (71.8m points)

python - Regexp to remove specific number of occurrences of character only

In Python re, I have long strings of text with > character chunks of different lengths. One string can have 3 consecutive > chars in the middle, >> in the beginning, or any such combination.

I want to write a regexp that, after splitting the string based on spaces, iterates through each word to only identify those regions with exactly 2 occurrences >>, and I can't be sure if it's at the beginning, middle or end of the whole string, or what characters are before or after it, or if it's even the only 2 characters in the string.

So far I could come up with:

word = re.sub(r'>{2}', '', word)

This ends up removing all occurrences of 2 or more. What regular expression would work for this requirement? Any help is appreciated.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You need to make sure there is no character of your choice both on the left and right using a pair of lookaround, a lookahead and a lookbehind. The general scheme is

(?<!X)X{n}(?!X)

where (?<!X) means no X immediately on the left is allowed, X{n} means n occurrences of X, and (?!X) means no X immediately on the right is allowed.

In this case, use

r'(?<!>)>{2}(?!>)'

See the regex demo.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...