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
  13 # The grammar file
  14 _GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "Grammar.txt")
  15 _PATTERN_GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "PatternGrammar.txt")
  16
  17
  18 class Symbols(object):
  19     def __init__(self, grammar):
  20         """Initializer.
  21
  22         Creates an attribute for each grammar symbol (nonterminal),
  23         whose value is the symbol's type (an int >= 256).
  24         """
  25         for name, symbol in grammar.symbol2number.items():
  26             setattr(self, name, symbol)
  27
  28
  29 def initialize(cache_dir=None):
  30     global python_grammar
  31     global python_grammar_no_print_statement
  32     global python_grammar_no_print_statement_no_exec_statement
  33     global python_grammar_no_print_statement_no_exec_statement_async_keywords
  34     global python_symbols
  35     global pattern_grammar
  36     global pattern_symbols
  37
  38     # Python 2
  39     python_grammar = driver.load_packaged_grammar("blib2to3", _GRAMMAR_FILE, cache_dir)
  40
  41     python_symbols = Symbols(python_grammar)
  42
  43     # Python 2 + from __future__ import print_function
  44     python_grammar_no_print_statement = python_grammar.copy()
  45     del python_grammar_no_print_statement.keywords["print"]
  46
  47     # Python 3.0-3.6
  48     python_grammar_no_print_statement_no_exec_statement = python_grammar.copy()
  49     del python_grammar_no_print_statement_no_exec_statement.keywords["print"]
  50     del python_grammar_no_print_statement_no_exec_statement.keywords["exec"]
  51
  52     # Python 3.7+
  53     python_grammar_no_print_statement_no_exec_statement_async_keywords = (
  54         python_grammar_no_print_statement_no_exec_statement.copy()
  55     )
  56     python_grammar_no_print_statement_no_exec_statement_async_keywords.async_keywords = (
  57         True
  58     )
  59
  60     pattern_grammar = driver.load_packaged_grammar(
  61         "blib2to3", _PATTERN_GRAMMAR_FILE, cache_dir
  62     )
  63     pattern_symbols = Symbols(pattern_grammar)