问题
I'm trying to parse some functions arguments with PyParsing but am having trouble getting the right syntax. Namely, given:
str = "(key=val())"
I would like the parser to return ['key', 'val()'].
I've been trying to get this to work with the following code; the .suppress() calls are intentionally omitted for clarity.
ob = Literal("(")
cb = Literal(")")
key = Word(alphas)
value = Word(alpha + "()")
parser = ob + key + "=" + value + cb
print parser.parseString(str)
but of course it's matching the final closing bracket as well and so I get a ParseException.
Is there an elegant solution to this? For example, I looked at nestedExpr but in this case it's not strictly a nesting since I want the val() to be treated as a literal. Similarly this question alludes to the problem but doesn't give a solution.
回答1:
Your definition of
value = Word(alpha + "()")
is overly liberal. Not only will it match trailing ()'s, but also any embedded ones, and regardless of matching opening and closing, values like:
SLDFJJ(sldkjf)
sdlkfj(sldkfj(lkskdjf)))(
and even just:
(((((())(()()()()
I suggest you define the syntax for an identifier, usually something like:
identifier = Word(alphas+'_', alphanums+'_')
and then compose value with:
value = Combine(identifier + '()')
Now the value expression won't erroneously accept any embedded ()s, and will only parse the trailing () and nothing further.
来源：https://stackoverflow.com/questions/35420067/capture-literal-brackets-inside-brackets-in-pyparsing