如何使用python2运行时与antlr4打印解析树

Question

我正在尝试使用antlr4版本4.4和python2运行时。语法来自antlr4书，第6页，文件:Hello.g4:

grammar Hello;           
r  : 'hello' ID ;
ID : [a-z]+ ;
WS : [ trn]+ -> skip ;

我用命令 生成词法分析器和解析器

antlr4 -Dlanguage=Python2 Hello.g4

然后生成

文件 hellohelper .py、HelloParser.py和 hellollistener .py等。我编写了一个主程序test.py来测试生成的python解析器:

from antlr4 import *
from HelloLexer import HelloLexer
from HelloParser import HelloParser
def main(argv):
    input = FileStream(argv[1])
    lexer = HelloLexer(input)
    stream = CommonTokenStream(lexer)
    parser = HelloParser(stream)
    tree = parser.r()
    print tree.toStringTree(parser)        <= the problem is here!
if __name__ == '__main__':
    import sys
    main(sys.argv)

除了无法打印解析树外，一切似乎都正常。

C:UsersLGantlrtpantlr2-codecodeinstall>Test.py data.txt
Traceback (most recent call last):
  File "C:UsersLGantlrtpantlr2-codecodeinstallTest.py", line 15, in <module>
    main(sys.argv)
  File "C:UsersLGantlrtpantlr2-codecodeinstallTest.py", line 11, in main
    print tree.toStringTree(parser)
  File "C:Python27libsite-packagesantlr4RuleContext.py", line 181, in toStringTree
    return Trees.toStringTree(self, ruleNames=ruleNames, recog=recog)
  File "C:Python27libsite-packagesantlr4treeTrees.py", line 48, in toStringTree
    s = escapeWhitespace(cls.getNodeText(t, ruleNames), False)
  File "C:Python27libsite-packagesantlr4treeTrees.py", line 68, in getNodeText
    return ruleNames[t.getRuleContext().getRuleIndex()]
TypeError: 'HelloParser' object does not support indexing

我还没弄明白是什么问题

Answer 1

奇怪的是，toStringTree是Python运行时中的一个类方法。您可以像这样调用它，以获得lisp风格的解析树，其中包括字符串化标记:

from antlr4 import *
from antlr4.tree.Trees import Trees
# import your parser & lexer here
# setup your lexer, stream, parser and tree like normal
print(Trees.toStringTree(tree, None, parser))
# the None is an optional rule names list

Answer 2

看起来您取错了toStringStree函数

看一下java文档

这解释了错误消息"object does not support indexing"。您选择的函数需要一个规则名称列表，而不是解析器。