cpython/Lib/__future__.py

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"""Record of phased-in incompatible language changes.
Each line is of the form:
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FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ")"
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.
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In the case of MandatoryReleases that have not yet occurred,
MandatoryRelease predicts the release in which the feature will become part
of the language.
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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.
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MandatoryRelease may also be None, meaning that a planned feature got
dropped.
Instances of class _Feature have two corresponding methods,
.getOptionalRelease() and .getMandatoryRelease().
No feature line is ever to be deleted from this file.
"""
class _Feature:
def __init__(self, optionalRelease, mandatoryRelease):
self.optional = optionalRelease
self.mandatory = mandatoryRelease
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(" + `self.getOptionalRelease()` + ", " + \
`self.getMandatoryRelease()` + ")"
nested_scopes = _Feature((2, 1, 0, "beta", 1), (2, 2, 0, "alpha", 0))
generators = _Feature((2, 2, 0, "alpha", 1), (2, 3, 0, "final", 0))