在python中的正则表达式匹配中连续转义字符串

Question

I met one problem when I use regex to match some string using Python.

Example string:

ln[1] --This is a string--

ln[2] Match the line below.

ln[3] --This is a string--

ln[4] Match this line start from here.

ln[5] -This is the end-

I want to extract abc in the string above.

code:

pattern = re.compile('%s(.*?)%s' % ('--This is a string--', '-This is the end-'))
re.findall(pattern, string)

How can I get the line 4 only, not get line 2 to line 4 ?

Thank you very much.

Answer 1

Probably, via this:

pattern = re.compile('.*(a.*?c)')
re.findall(pattern, string)  # yields ["abc"]

Answer 2

>>> re.findall('a[^a]*c', 'aaaaaaaaabc')
['abc']
>>> re.findall('a[^a]*c', 'aaaaaaaaa c')
['a c']

Answer 3

If you want to replace all instances of repeated characters you could use id or named groups.

Example:

with id:

>>> re.sub('(.)(\\1)+', '\\1', 'abcAAAAabcBBBBabcCCCCabc')
'abcAabcBabcCabc'

with name:

>>> re.sub('(?P<n>.)(?P=n)+', '\\1', 'abcAAAAabcBBBBabcCCCCabc')
'abcAabcBabcCabc'