I need to define a grammar to parse the code below:

P1 ATTACKS p2 // P1 represents a pawn in chess game and p2 represents an opponent pawn

OR

P1 DEFENDS P2

OR

P1 IATTACKS p2,p3

OR

P1 IDEFENDS P2,P3

In order to do that I wrote the Python code below:

import pypeg2 as g

// actor() is a symbol representing a piece of chess game and a number associated to it
def actor(): return g.re.compile(r"[KQRNBPFS]d", g.re.IGNORECASE)

// this class is a symbol which defines a kind of action in chess game between two or more pieces, IATTACKS means INDIRECT ATTACK and so on

class SceneryAction(str):
    grammar = g.Enum(g.K("ATTACKS"), g.K("DEFENDS"), g.K("IATTACKS"), g.K("IDEFENDS")) 

// this class represents an action occurring and must be parsed as an actor (piece) doing some action over another actor (piece)

class SceneryFrame(str):
    grammar = actor(), SceneryAction(), (actor(), g.csl(actor())), g.endl

The final goal of this grammar is to define a language for pattern representation in chess games.

However, when I try to parse this line:

k = g.parse("P1 ATTACKS p1n",SceneryFrame)

I got this error:

  File "d:DocumentsProjectsPythonStratVisionPATLANParser.py", line 62, in <module>
    k = g.parse("P1 ATTACKS p1n",SceneryFrame)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:PythonLibsite-packagespypeg2__init__.py", line 667, in parse
    t, r = parser.parse(text, thing)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:PythonLibsite-packagespypeg2__init__.py", line 794, in parse
    raise r
  File "<string>", line 1
    P1
       ^
SyntaxError: expecting match on [KQRNBPFS]d