blib2to3/pygram.py

   1 # Copyright 2006 Google, Inc. All Rights Reserved.
   2 # Licensed to PSF under a Contributor Agreement.
   3
   4 """Export the Python grammar and symbols."""
   5
   6 # Python imports
   7 import os
   8
   9 # Local imports
  10 from .pgen2 import token
  11 from .pgen2 import driver
  12 from . import pytree
  13
  14 # The grammar file
  15 _GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "Grammar.txt")
  16 _PATTERN_GRAMMAR_FILE = os.path.join(os.path.dirname(__file__),
  17                                      "PatternGrammar.txt")
  18
  19
  20 class Symbols(object):
  21
  22     def __init__(self, grammar):
  23         """Initializer.
  24
  25         Creates an attribute for each grammar symbol (nonterminal),
  26         whose value is the symbol's type (an int >= 256).
  27         """
  28         for name, symbol in grammar.symbol2number.items():
  29             setattr(self, name, symbol)
  30
  31
  32 def initialize(cache_dir=None):
  33     global python_grammar
  34     global python_grammar_no_print_statement
  35     global python_grammar_no_print_statement_no_exec_statement
  36     global python_symbols
  37     global pattern_grammar
  38     global pattern_symbols
  39
  40     # Python 2
  41     python_grammar = driver.load_packaged_grammar("blib2to3", _GRAMMAR_FILE,
  42                                                   cache_dir)
  43
  44     python_symbols = Symbols(python_grammar)
  45
  46     # Python 2 + from __future__ import print_function
  47     python_grammar_no_print_statement = python_grammar.copy()
  48     del python_grammar_no_print_statement.keywords["print"]
  49
  50     # Python 3
  51     python_grammar_no_print_statement_no_exec_statement = python_grammar.copy()
  52     del python_grammar_no_print_statement_no_exec_statement.keywords["print"]
  53     del python_grammar_no_print_statement_no_exec_statement.keywords["exec"]
  54
  55     pattern_grammar = driver.load_packaged_grammar("blib2to3", _PATTERN_GRAMMAR_FILE,
  56                                                    cache_dir)
  57     pattern_symbols = Symbols(pattern_grammar)