带有\\ +？=的正则表达式无法正常工作/转义'+'

Question

I have the following code:

import re
pattern = r'.className\s*\+?=\s*.*?\+?[\'"](.*?)["\']'
code_str = "if (El.className == 'blue' ) {\nEl.className = 'className20';\n}\n"
re.findall(pattern, code_str)

Output >>> ['blue', 'className20']

I am only wanting the output ['className20'] .

[ Update ] It also needs to handle this concatenation case where some_str is combined with className20 . It should still only return ['className20'] .

code_str2 = "if (El.className == 'blue' ) {\nEl.className = some_str + 'className20';\n}\n"
re.findall(pattern, code_str)

I've also tried.

pattern = r'.className\s*\+{,1}={1}\s*.*?\+?[\'"](.*?)["\']'
pattern = r'.className\s*\+?[=]{1}\s*.*?\+?[\'"](.*?)["\']'

Any insight is welcomed. The problem seems to be that == appears in code_str . The pattern I'm using is too greedy. My understanding is that \\+ is properly escaping the + sign, but I could be wrong.

Answer 1

Why is there a .*? after =\\s* ? You want to allow anything to follow an equals followed by any amount of space? That's what allows == 'blue' to be accepted; the \\s* does nothing, but the following .*? is matching the = following the first = . Drop it, and it works:

import re
pattern = r'.className\s*\+?=\s*\+?[\'"](.*?)["\']'
code_str = "if (El.className == 'blue' ) {\nEl.className = 'className20';\n}\n"
re.findall(pattern, code_str)

producing ['className20'] as expected. The question is whether there was some reason to allow arbitrary characters there.