Lib/__future__.py

   1 """Record of phased-in incompatible language changes.
   2
   3 Each line is of the form:
   4
   5     FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
   6                               CompilerFlag ")"
   7
   8 where, normally, OptionalRelease < MandatoryRelease, and both are 5-tuples
   9 of the same form as sys.version_info:
  10
  11     (PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
  12      PY_MINOR_VERSION, # the 1; an int
  13      PY_MICRO_VERSION, # the 0; an int
  14      PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
  15      PY_RELEASE_SERIAL # the 3; an int
  16     )
  17
  18 OptionalRelease records the first release in which
  19
  20     from __future__ import FeatureName
  21
  22 was accepted.
  23
  24 In the case of MandatoryReleases that have not yet occurred,
  25 MandatoryRelease predicts the release in which the feature will become part
  26 of the language.
  27
  28 Else MandatoryRelease records when the feature became part of the language;
  29 in releases at or after that, modules no longer need
  30
  31     from __future__ import FeatureName
  32
  33 to use the feature in question, but may continue to use such imports.
  34
  35 MandatoryRelease may also be None, meaning that a planned feature got
  36 dropped.
  37
  38 Instances of class _Feature have two corresponding methods,
  39 .getOptionalRelease() and .getMandatoryRelease().
  40
  41 CompilerFlag is the (bitfield) flag that should be passed in the fourth
  42 argument to the builtin function compile() to enable the feature in
  43 dynamically compiled code.  This flag is stored in the .compiler_flag
  44 attribute on _Future instances.  These values must match the appropriate
  45 #defines of CO_xxx flags in Include/compile.h.
  46
  47 No feature line is ever to be deleted from this file.
  48 """
  49
  50 all_feature_names = [
  51     "nested_scopes",
  52     "generators",
  53     "division",
  54     "absolute_import",
  55     "with_statement",
  56     "print_function",
  57     "unicode_literals",
  58     "barry_as_FLUFL",
  59 ]
  60
  61 __all__ = ["all_feature_names"] + all_feature_names
  62
  63 # The CO_xxx symbols are defined here under the same names used by
  64 # compile.h, so that an editor search will find them here.  However,
  65 # they're not exported in __all__, because they don't really belong to
  66 # this module.
  67 CO_NESTED            = 0x0010   # nested_scopes
  68 CO_GENERATOR_ALLOWED = 0        # generators (obsolete, was 0x1000)
  69 CO_FUTURE_DIVISION   = 0x2000   # division
  70 CO_FUTURE_ABSOLUTE_IMPORT = 0x4000 # perform absolute imports by default
  71 CO_FUTURE_WITH_STATEMENT  = 0x8000   # with statement
  72 CO_FUTURE_PRINT_FUNCTION  = 0x10000   # print function
  73 CO_FUTURE_UNICODE_LITERALS = 0x20000 # unicode string literals
  74 CO_FUTURE_BARRY_AS_BDFL = 0x40000
  75
  76 class _Feature:
  77     def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
  78         self.optional = optionalRelease
  79         self.mandatory = mandatoryRelease
  80         self.compiler_flag = compiler_flag
  81
  82     def getOptionalRelease(self):
  83         """Return first release in which this feature was recognized.
  84
  85         This is a 5-tuple, of the same form as sys.version_info.
  86         """
  87
  88         return self.optional
  89
  90     def getMandatoryRelease(self):
  91         """Return release in which this feature will become mandatory.
  92
  93         This is a 5-tuple, of the same form as sys.version_info, or, if
  94         the feature was dropped, is None.
  95         """
  96
  97         return self.mandatory
  98
  99     def __repr__(self):
 100         return "_Feature" + repr((self.optional,
 101                                   self.mandatory,
 102                                   self.compiler_flag))
 103
 104 nested_scopes = _Feature((2, 1, 0, "beta",  1),
 105                          (2, 2, 0, "alpha", 0),
 106                          CO_NESTED)
 107
 108 generators = _Feature((2, 2, 0, "alpha", 1),
 109                       (2, 3, 0, "final", 0),
 110                       CO_GENERATOR_ALLOWED)
 111
 112 division = _Feature((2, 2, 0, "alpha", 2),
 113                     (3, 0, 0, "alpha", 0),
 114                     CO_FUTURE_DIVISION)
 115
 116 absolute_import = _Feature((2, 5, 0, "alpha", 1),
 117                            (2, 7, 0, "alpha", 0),
 118                            CO_FUTURE_ABSOLUTE_IMPORT)
 119
 120 with_statement = _Feature((2, 5, 0, "alpha", 1),
 121                           (2, 6, 0, "alpha", 0),
 122                           CO_FUTURE_WITH_STATEMENT)
 123
 124 print_function = _Feature((2, 6, 0, "alpha", 2),
 125                           (3, 0, 0, "alpha", 0),
 126                           CO_FUTURE_PRINT_FUNCTION)
 127
 128 unicode_literals = _Feature((2, 6, 0, "alpha", 2),
 129                             (3, 0, 0, "alpha", 0),
 130                             CO_FUTURE_UNICODE_LITERALS)
 131
 132 barry_as_FLUFL = _Feature((3, 1, 0, "alpha", 2),
 133                          (3, 9, 0, "alpha", 0),
 134                          CO_FUTURE_BARRY_AS_BDFL)