__future__.py

"""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)