检测未包含在双引号中的符号（正则表达式）

Question

I'd like to design a regex that can mmatch the characters [].\\,();~- that are not enclosed within double quotes.

For example, this string:

do Output.printString("Test 1: expected result: 5; actual result: ");

should return matches:

['.', '(', ')', ';']

I tried using negative lookahead and negative lookbehind to no avail.

Answer 1

You can use this regex with a lookahead that makes sure to match a symbol outside pair of double quotes:

>>> s = 'do Output.printString("Test 1: expected result: 5; actual result: ");'
>>> print re.findall(r'[][.,();~-](?=(?:(?:[^"]*"){2})*[^"]*$)', s)
['.', '(', ')', ';']

RegEx Demo

• This regex will split on given special characters if those are outside double quotes by using a lookahead to make sure there are even number of quotes after matched character.
• (?:[^"]*"){2} finds a pair of quotes
• (?:(?:[^"]*"){2})* finds 0 or more such pairs
• [^"]*$ makes sure that we don't have any more quotes after last matched quote

Answer 2

You need two steps, as Python regular expressions are not powerful enough to do it in one go.

re.findall(r'[\[\].\\,();~-]', re.sub(r'"(?:\\.|[^"\\])*"', '', s))
# => ['.', '(', ')', ';']

The inner re.sub deletes all double-quoted strings (ignoring escaped double quotes); then you can use re.findall to easily pick up what you want.

Answer 3

We could do something like -

Remove text inside double quotes

import re
pattern = u"[\"].*?[\"]"
text = 'do Output.printString("Test 1: expected result: 5; actual result: ");'
new_text = re.sub(ptrn, '', text)
# O/P 'do Output.printString();'

Match all characters you need

pattern_2 = u"[\[\]\.\,\(\)\;\~\-]"
matches = re.findall(pattern2, new_text)

O/P ['.', '(', ')', ';']