Any parser generator available?

[Rick Lee]

The Python Library contains a fair number of parsers for specific
syntaxes like XML, HTML, URL, etc.

However, I am looking for a parser generator that can generate a parser
from a grammar description.  The Python Parser in the Python Language
Services in the Library may have been built from a parser generator,
because the documentation refers to a GRAMMAR file in the standard
distribution.  However, the documentation did not mention a parser
generator.

The grammar that I like to parse is quite simple, compared to a
programming language like Python.  My interest for a parser generator is
so that I don't have to implement a parser (not that I know how to do it
well), and also because the grammar, though simple, will change a lot in
its life time (new statements get added).  For those who might know, the
grammar that I like to have a parser for is a set of TL1 commands.  TL1
is a meta-grammar, so to speak, that is fairly commonly used in the
telecom industry.

Thanks in advance.

- Rick Lee
  rwklee at home.com