정규식과 파이파싱을 사용하여 Python에서 중첩된 괄호를 어떻게 효과적으로 추출할 수 있습니까?

<code class="python">import pyparsing # make sure you have this installed

thecontent = pyparsing.Word(pyparsing.alphanums) | '+' | '-'
parens     = pyparsing.nestedExpr( '(', ')', content=thecontent)</code>

<code class="python">>>> parens.parseString("((a + b) + c)")</code>

(                          # all of str
 [
  (                        # ((a + b) + c)
   [
    (                      #  (a + b)
     ['a', '+', 'b'], {}   
    ),                     #  (a + b)      [closed]
    '+',
    'c'
   ], {}
  )                        # ((a + b) + c) [closed]
 ], {}  
)                          # all of str    [closed]

<code class="python">res = parens.parseString("((12 + 2) + 3)")
res.asList()</code>

[[['12', '+', '2'], '+', '3']]