在我的 Python 应用程序中，我需要编写一个正则表达式来匹配以分号 ( ) 终止的 C++for或循环。例如，它应该匹配这个：while``;

for (int i = 0; i < 10; i++);

…但不是这个：

for (int i = 0; i < 10; i++)

乍一看，这看起来微不足道，直到您意识到左括号和右括号之间的文本可能包含其他括号，例如：

for (int i = funcA(); i < funcB(); i++);

我正在使用 python.re 模块。现在我的正则表达式看起来像这样（我留下了我的评论，以便您更容易理解）：

# match any line that begins with a "for" or "while" statement:
^\s*(for|while)\s*
\(  # match the initial opening parenthesis
    # Now make a named group 'balanced' which matches a balanced substring.
    (?P<balanced>
        # A balanced substring is either something that is not a parenthesis:
        [^()]
        | # …or a parenthesised string:
        \( # A parenthesised string begins with an opening parenthesis
            (?P=balanced)* # …followed by a sequence of balanced substrings
        \) # …and ends with a closing parenthesis
    )*  # Look for a sequence of balanced substrings
\)  # Finally, the outer closing parenthesis.
# must end with a semi-colon to match:
\s*;\s*

这对于上述所有情况都非常有效，但是一旦您尝试使 for 循环的第三部分包含一个函数，它就会中断，如下所示：

for (int i = 0; i < 10; doSomethingTo(i));

我认为它会中断，因为一旦您在左括号和右括号之间放置一些文本，“平衡”组就会匹配包含文本，因此该(?P=balanced)部分不再起作用，因为它不匹配（由于事实括号内的文字不同）。

在我的 Python 代码中，我使用了 VERBOSE 和 MULTILINE 标志，并像这样创建正则表达式：

REGEX_STR = r"""# match any line that begins with a "for" or "while" statement:
^\s*(for|while)\s*
\(  # match the initial opening parenthesis
    # Now make a named group 'balanced' which matches
    # a balanced substring.
    (?P<balanced>
        # A balanced substring is either something that is not a parenthesis:
        [^()]
        | # …or a parenthesised string:
        \( # A parenthesised string begins with an opening parenthesis
            (?P=balanced)* # …followed by a sequence of balanced substrings
        \) # …and ends with a closing parenthesis
    )*  # Look for a sequence of balanced substrings
\)  # Finally, the outer closing parenthesis.
# must end with a semi-colon to match:
\s*;\s*"""

REGEX_OBJ = re.compile(REGEX_STR, re.MULTILINE| re.VERBOSE)

任何人都可以建议改进这个正则表达式吗？这对我来说太复杂了，无法理解。