__future__

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.