缺少使用Python目标的ANTLR4中的Lexer方法？

Question

I am trying to use ANTLR4 with Python2 Target. As I understand it, semantic predicates of the following form are code from the target language embedded in the grammar. For example, I have one such rule:

'S' {getCharPositionInLine() == 1}? 'OMETHING'

This basically is to ensure that the token SOMETHING begins at the start of the line (otherwise it is something else). I used the Java target (default), because its testing facilities are better than in Python. So far so good. However once my grammar was working, upon trying to translate this code to Python, I come across a problem. Firstly I assume that the above code in Java (I don't know much Java at all) is the calling of the class method getCharPositionInLine , so naturally it seems reasonable to translate the above to:

'S' {self.getCharPositionInLine() == 1}? 'OMETHING'

However I ultimately get the error:

'MyLexer' object has no attribute 'getCharPositionInLine'

And I go and check the Lexer.py files (which MyLexer inherits from) in both antlr4/runtime/Python2/ and antlr4/runtime/Python3/ , and lo and behold, there is no such method. I didn't realise certain targets were missing features. Having known nothing about parsers and lexers before this I was very proud of my grammar but after all this I might not even be able to use it! Is there any way I can work around this?

Answer 1

As I understand python runtimes use column property instead of getCharPositionInLine . See also: https://github.com/antlr/antlr4/blob/4.6/runtime/Python2/src/antlr4/Lexer.py#L237