Python-获取字符串中当前和下一个模式出现之间的内容

Question

I want to implement the following in python

(1)Search pattern in a string

(2)Get content till next occurence of the same pattern in the same string

Till end of the string do (1) and (2)

Searched all available answers but of no use.

Thanks in advance.

Answer 1

You can use something like this

re.findall(r"pattern.*?(?=pattern|$)",test_Str)

Here we search pattern and with lookahead make sure it captures till next pattern or end of string .

Answer 2

As mentioned by Blckknght in the comment, you can achieve this with re.split . re.split retains all empty strings between a) the beginning of the string and the first match, b) the last match and the end of the string and c) between different matches:

>>> re.split('abc', 'abcabcabcabc')
['', '', '', '', '']
>>> re.split('bca', 'abcabcabcabc')
['a', '', '', 'bc']
>>> re.split('c', 'abcabcabcabc')
['ab', 'ab', 'ab', 'ab', '']
>>> re.split('a', 'abcabcabcabc')
['', 'bc', 'bc', 'bc', 'bc']

If you want to retain only c) the strings between 2 matches of the pattern, just slice the resulting array with [1:-1] .

Do note that there are two caveat with this method:

1. re.split doesn't split on empty string match.

    >>> re.split('', 'abcabc') ['abcabc']

2. Content in capturing groups will be included in the resulting array.

    >>> re.split(r'(.)(?!\\1)', 'aaaaaakkkkkkbbbbbsssss') ['aaaaa', 'a', 'kkkkk', 'k', 'bbbb', 'b', 'ssss', 's', '']

You have to write your own function with finditer if you need to handle those use cases.

This is the variant where only case c) is matched.

def findbetween(pattern, input):
    out = []
    start = 0
    for m in re.finditer(pattern, input):
        out.append(input[start:m.start()])
        start = m.end()
    return out

Sample run:

>>> findbetween('abc', 'abcabcabcabc')
['', '', '']
>>> findbetween(r'', 'abcdef')
['a', 'b', 'c', 'd', 'e', 'f']
>>> findbetween(r'ab', 'abcabcabc')
['c', 'c']
>>> findbetween(r'b', 'abcabcabc')
['ca', 'ca']
>>> findbetween(r'(?<=(.))(?!\1)', 'aaaaaaaaaaaabbbbbbbbbbbbkkkkkkk')
['bbbbbbbbbbbb', 'kkkkkkk']

(In the last example, (?<=(.))(?!\\1) matches the empty string at the end of the string, so 'kkkkkkk' is included in the list of results)