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- IMPORT_NAME takes an extra argument from the stack: the relativeness of the import. Only passed to __import__ when it's not -1. - __import__() takes an optional 5th argument for the same thing; it __defaults to -1 (old semantics: try relative, then absolute) - 'from . import name' imports name (be it module or regular attribute) from the current module's *package*. Likewise, 'from .module import name' will import name from a sibling to the current module. - Importing from outside a package is not allowed; 'from . import sys' in a toplevel module will not work, nor will 'from .. import sys' in a (single-level) package. - 'from __future__ import absolute_import' will turn on the new semantics for import and from-import: imports will be absolute, except for from-import with dots. Includes tests for regular imports and importhooks, parser changes and a NEWS item, but no compiler-package changes or documentation changes.
111 lines
3.6 KiB
Python
111 lines
3.6 KiB
Python
"""Record of phased-in incompatible language changes.
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Each line is of the form:
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FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
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CompilerFlag ")"
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where, normally, OptionalRelease < MandatoryRelease, and both are 5-tuples
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of the same form as sys.version_info:
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(PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
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PY_MINOR_VERSION, # the 1; an int
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PY_MICRO_VERSION, # the 0; an int
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PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
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PY_RELEASE_SERIAL # the 3; an int
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)
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OptionalRelease records the first release in which
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from __future__ import FeatureName
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was accepted.
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In the case of MandatoryReleases that have not yet occurred,
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MandatoryRelease predicts the release in which the feature will become part
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of the language.
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Else MandatoryRelease records when the feature became part of the language;
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in releases at or after that, modules no longer need
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from __future__ import FeatureName
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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
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dropped.
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Instances of class _Feature have two corresponding methods,
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.getOptionalRelease() and .getMandatoryRelease().
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CompilerFlag is the (bitfield) flag that should be passed in the fourth
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argument to the builtin function compile() to enable the feature in
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dynamically compiled code. This flag is stored in the .compiler_flag
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attribute on _Future instances. These values must match the appropriate
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#defines of CO_xxx flags in Include/compile.h.
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No feature line is ever to be deleted from this file.
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"""
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all_feature_names = [
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"nested_scopes",
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"generators",
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"division",
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"absolute_import",
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]
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__all__ = ["all_feature_names"] + all_feature_names
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# The CO_xxx symbols are defined here under the same names used by
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# compile.h, so that an editor search will find them here. However,
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# they're not exported in __all__, because they don't really belong to
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# this module.
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CO_NESTED = 0x0010 # nested_scopes
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CO_GENERATOR_ALLOWED = 0 # generators (obsolete, was 0x1000)
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CO_FUTURE_DIVISION = 0x2000 # division
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CO_FUTURE_ABSIMPORT = 0x4000 # absolute_import
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class _Feature:
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def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
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self.optional = optionalRelease
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self.mandatory = mandatoryRelease
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self.compiler_flag = compiler_flag
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def getOptionalRelease(self):
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"""Return first release in which this feature was recognized.
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This is a 5-tuple, of the same form as sys.version_info.
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"""
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return self.optional
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def getMandatoryRelease(self):
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"""Return release in which this feature will become mandatory.
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This is a 5-tuple, of the same form as sys.version_info, or, if
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the feature was dropped, is None.
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"""
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return self.mandatory
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def __repr__(self):
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return "_Feature" + repr((self.optional,
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self.mandatory,
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self.compiler_flag))
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nested_scopes = _Feature((2, 1, 0, "beta", 1),
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(2, 2, 0, "alpha", 0),
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CO_NESTED)
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generators = _Feature((2, 2, 0, "alpha", 1),
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(2, 3, 0, "final", 0),
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CO_GENERATOR_ALLOWED)
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division = _Feature((2, 2, 0, "alpha", 2),
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(3, 0, 0, "alpha", 0),
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CO_FUTURE_DIVISION)
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absolute_import = _Feature((2, 5, 0, "alpha", 1),
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(2, 7, 0, "alpha", 0),
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CO_FUTURE_ABSIMPORT)
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