Lib/regex_syntax.py

   1 """Constants for selecting regexp syntaxes for the obsolete regex module.
   2
   3 This module is only for backward compatibility.  "regex" has now
   4 been replaced by the new regular expression module, "re".
   5
   6 These bits are passed to regex.set_syntax() to choose among
   7 alternative regexp syntaxes.
   8 """
   9
  10 # 1 means plain parentheses serve as grouping, and backslash
  11 #   parentheses are needed for literal searching.
  12 # 0 means backslash-parentheses are grouping, and plain parentheses
  13 #   are for literal searching.
  14 RE_NO_BK_PARENS = 1
  15
  16 # 1 means plain | serves as the "or"-operator, and \| is a literal.
  17 # 0 means \| serves as the "or"-operator, and | is a literal.
  18 RE_NO_BK_VBAR = 2
  19
  20 # 0 means plain + or ? serves as an operator, and \+, \? are literals.
  21 # 1 means \+, \? are operators and plain +, ? are literals.
  22 RE_BK_PLUS_QM = 4
  23
  24 # 1 means | binds tighter than ^ or $.
  25 # 0 means the contrary.
  26 RE_TIGHT_VBAR = 8
  27
  28 # 1 means treat \n as an _OR operator
  29 # 0 means treat it as a normal character
  30 RE_NEWLINE_OR = 16
  31
  32 # 0 means that a special characters (such as *, ^, and $) always have
  33 #   their special meaning regardless of the surrounding context.
  34 # 1 means that special characters may act as normal characters in some
  35 #   contexts.  Specifically, this applies to:
  36 #       ^ - only special at the beginning, or after ( or |
  37 #       $ - only special at the end, or before ) or |
  38 #       *, +, ? - only special when not after the beginning, (, or |
  39 RE_CONTEXT_INDEP_OPS = 32
  40
  41 # ANSI sequences (\n etc) and \xhh
  42 RE_ANSI_HEX = 64
  43
  44 # No GNU extensions
  45 RE_NO_GNU_EXTENSIONS = 128
  46
  47 # Now define combinations of bits for the standard possibilities.
  48 RE_SYNTAX_AWK = (RE_NO_BK_PARENS | RE_NO_BK_VBAR | RE_CONTEXT_INDEP_OPS)
  49 RE_SYNTAX_EGREP = (RE_SYNTAX_AWK | RE_NEWLINE_OR)
  50 RE_SYNTAX_GREP = (RE_BK_PLUS_QM | RE_NEWLINE_OR)
  51 RE_SYNTAX_EMACS = 0
  52
  53 # (Python's obsolete "regexp" module used a syntax similar to awk.)