正则表达式搜索对括号在python中的不同行

Question

This is the example string in a file I work with:

apple (sweet
   fruit) at home

If I want to find anything between parenthesis and remove it, how to do it? This is the result that I expect for:

apple at home

I tried below but it doesn't work as above lines are two different lines.

re.sub(r'\(\s*([^)]+)\)', '', line)

Answer 1

Try:

re.sub(r'\s*\([^)]+\)', '', line)

In a python regex, ( and ) are normally used for grouping. Because you want to match literal parens, not do grouping, we replace ( by \\( and we replace ) by \\) .

Example:

>>> print(line)
apple (sweet

      fruit) at home
>>> import re
>>> re.sub(r'\s*\([^)]+\)', '', line)
'apple at home'

Issues with reading a multiline string from a file

Using the read method, we can successfully do the multiline substitution:

>>> import re
>>> line = open('File').read()
>>> print(line)
apple (sweet
   fruit) at home

>>> re.sub(r'\s*\([^)]+\)', '', line)
'apple at home\n'

If we use the readlines methods, though, we have problems:

>>> line = open('File').readlines()
>>> print(line)
['apple (sweet\n', '   fruit) at home\n']

readlines creates a list of lines. re.sub requires a string not a list. Therefore, we need to use join to get a successful substitution:

>>> re.sub(r'\s*\([^)]+\)', '', ''.join(line))
'apple at home\n'

Answer 2

You'll need to use re.MULTILINE and non-greedy match.

re.sub(r'\(.+?\)', '', line, re.MULTILINE)

Reference: https://docs.python.org/2/library/re.html