Lib/lib2to3/pygram.py

# Copyright 2006 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.

"""Export the Python grammar and symbols."""

# Python imports
import os

# Local imports
from .pgen2 import token
from .pgen2 import driver
from . import pytree

# The grammar file
_GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "Grammar.txt")


class Symbols(object):

    def __init__(self, grammar):
        """Initializer.

        Creates an attribute for each grammar symbol (nonterminal),
        whose value is the symbol's type (an int >= 256).
        """
        for name, symbol in grammar.symbol2number.iteritems():
            setattr(self, name, symbol)


python_grammar = driver.load_grammar(_GRAMMAR_FILE)
python_symbols = Symbols(python_grammar)


def parenthesize(node):
    return pytree.Node(python_symbols.atom,
                       (pytree.Leaf(token.LPAR, "("),
                        node,
                        pytree.Leaf(token.RPAR, ")")))