如何使用pyparsing来解析具有多个开启/关闭类型的嵌套表达式？

Question

我想使用pyparsing来解析表单的表达式:expr = '(gimme [some {nested [lists]}])',并返回一个表单的python列表:[[['gimme', ['some', ['nested', ['lists']]]]]].现在我的语法看起来像这样:

nestedParens = nestedExpr('(',')')
nestedBrackets = nestedExpr('[',']')
nestedCurlies = nestedExpr('{','}')
included = nestedParens | nestedBrackets | nestedCurlies

目前, enclosed.searchString(expr)返回一个表单列表:[[['gimme', ['some', '{nested', '[lists]}']]]].这不是我想要的,因为它不能识别正方形或花括号,但我不知道为什么.

Answer 1

这是一个使用自修改语法动态匹配正确的右括号字符的pyparsing解决方案.

from pyparsing import *

data = '(gimme [some {nested, nested [lists]}])'

opening = oneOf("( { [")
nonBracePrintables = ''.join(c for c in printables if c not in '(){}[]')
closingFor = dict(zip("({[",")}]"))
closing = Forward()
# initialize closing with an expression
closing << NoMatch()
closingStack = []
def pushClosing(t):
    closingStack.append(closing.expr)
    closing << Literal( closingFor[t[0]] )
def popClosing():
    closing << closingStack.pop()
opening.setParseAction(pushClosing)
closing.setParseAction(popClosing)

matchedNesting = nestedExpr( opening, closing, Word(alphas) | Word(nonBracePrintables) )

print matchedNesting.parseString(data).asList()

打印:

[['gimme', ['some', ['nested', ',', 'nested', ['lists']]]]]

更新:我发布了上述解决方案,因为我实际上是在一年前写的.我只是仔细看看你原来的帖子,它让我想到了这个operatorPrecedence方法创建的递归类型定义,所以我使用你原来的方法重新编写这个解决方案 - 更容易理解!(可能有正确的输入数据的左递归问题,但未经过全面测试):

from pyparsing import *

enclosed = Forward()
nestedParens = nestedExpr('(', ')', content=enclosed) 
nestedBrackets = nestedExpr('[', ']', content=enclosed) 
nestedCurlies = nestedExpr('{', '}', content=enclosed) 
enclosed << (Word(alphas) | ',' | nestedParens | nestedBrackets | nestedCurlies)


data = '(gimme [some {nested, nested [lists]}])' 

print enclosed.parseString(data).asList()

得到:

[['gimme', ['some', ['nested', ',', 'nested', ['lists']]]]]