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+"""Record of phased-in incompatible language changes.
+
+Each line is of the form:
+
+ FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
+ CompilerFlag ")"
+
+where, normally, OptionalRelease < MandatoryRelease, and both are 5-tuples
+of the same form as sys.version_info:
+
+ (PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
+ PY_MINOR_VERSION, # the 1; an int
+ PY_MICRO_VERSION, # the 0; an int
+ PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
+ PY_RELEASE_SERIAL # the 3; an int
+ )
+
+OptionalRelease records the first release in which
+
+ from __future__ import FeatureName
+
+was accepted.
+
+In the case of MandatoryReleases that have not yet occurred,
+MandatoryRelease predicts the release in which the feature will become part
+of the language.
+
+Else MandatoryRelease records when the feature became part of the language;
+in releases at or after that, modules no longer need
+
+ from __future__ import FeatureName
+
+to use the feature in question, but may continue to use such imports.
+
+MandatoryRelease may also be None, meaning that a planned feature got
+dropped.
+
+Instances of class _Feature have two corresponding methods,
+.getOptionalRelease() and .getMandatoryRelease().
+
+CompilerFlag is the (bitfield) flag that should be passed in the fourth
+argument to the builtin function compile() to enable the feature in
+dynamically compiled code. This flag is stored in the .compiler_flag
+attribute on _Future instances. These values must match the appropriate
+#defines of CO_xxx flags in Include/compile.h.
+
+No feature line is ever to be deleted from this file.
+"""
+
+all_feature_names = [
+ "nested_scopes",
+ "generators",
+ "division",
+ "absolute_import",
+ "with_statement",
+ "print_function",
+ "unicode_literals",
+]
+
+__all__ = ["all_feature_names"] + all_feature_names
+
+# The CO_xxx symbols are defined here under the same names used by
+# compile.h, so that an editor search will find them here. However,
+# they're not exported in __all__, because they don't really belong to
+# this module.
+CO_NESTED = 0x0010 # nested_scopes
+CO_GENERATOR_ALLOWED = 0 # generators (obsolete, was 0x1000)
+CO_FUTURE_DIVISION = 0x2000 # division
+CO_FUTURE_ABSOLUTE_IMPORT = 0x4000 # perform absolute imports by default
+CO_FUTURE_WITH_STATEMENT = 0x8000 # with statement
+CO_FUTURE_PRINT_FUNCTION = 0x10000 # print function
+CO_FUTURE_UNICODE_LITERALS = 0x20000 # unicode string literals
+
+class _Feature:
+ def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
+ self.optional = optionalRelease
+ self.mandatory = mandatoryRelease
+ self.compiler_flag = compiler_flag
+
+ def getOptionalRelease(self):
+ """Return first release in which this feature was recognized.
+
+ This is a 5-tuple, of the same form as sys.version_info.
+ """
+
+ return self.optional
+
+ def getMandatoryRelease(self):
+ """Return release in which this feature will become mandatory.
+
+ This is a 5-tuple, of the same form as sys.version_info, or, if
+ the feature was dropped, is None.
+ """
+
+ return self.mandatory
+
+ def __repr__(self):
+ return "_Feature" + repr((self.optional,
+ self.mandatory,
+ self.compiler_flag))
+
+nested_scopes = _Feature((2, 1, 0, "beta", 1),
+ (2, 2, 0, "alpha", 0),
+ CO_NESTED)
+
+generators = _Feature((2, 2, 0, "alpha", 1),
+ (2, 3, 0, "final", 0),
+ CO_GENERATOR_ALLOWED)
+
+division = _Feature((2, 2, 0, "alpha", 2),
+ (3, 0, 0, "alpha", 0),
+ CO_FUTURE_DIVISION)
+
+absolute_import = _Feature((2, 5, 0, "alpha", 1),
+ (3, 0, 0, "alpha", 0),
+ CO_FUTURE_ABSOLUTE_IMPORT)
+
+with_statement = _Feature((2, 5, 0, "alpha", 1),
+ (2, 6, 0, "alpha", 0),
+ CO_FUTURE_WITH_STATEMENT)
+
+print_function = _Feature((2, 6, 0, "alpha", 2),
+ (3, 0, 0, "alpha", 0),
+ CO_FUTURE_PRINT_FUNCTION)
+
+unicode_literals = _Feature((2, 6, 0, "alpha", 2),
+ (3, 0, 0, "alpha", 0),
+ CO_FUTURE_UNICODE_LITERALS)