Misc. changes, including documenting the ability to specify a class attribute in...
[python.git] / Lib / __future__.py
blob8940a95aeee36f4e8be9e8be2ca92511795c78b3
1 """Record of phased-in incompatible language changes.
3 Each line is of the form:
5 FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
6 CompilerFlag ")"
8 where, normally, OptionalRelease < MandatoryRelease, and both are 5-tuples
9 of the same form as sys.version_info:
11 (PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
12 PY_MINOR_VERSION, # the 1; an int
13 PY_MICRO_VERSION, # the 0; an int
14 PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
15 PY_RELEASE_SERIAL # the 3; an int
18 OptionalRelease records the first release in which
20 from __future__ import FeatureName
22 was accepted.
24 In the case of MandatoryReleases that have not yet occurred,
25 MandatoryRelease predicts the release in which the feature will become part
26 of the language.
28 Else MandatoryRelease records when the feature became part of the language;
29 in releases at or after that, modules no longer need
31 from __future__ import FeatureName
33 to use the feature in question, but may continue to use such imports.
35 MandatoryRelease may also be None, meaning that a planned feature got
36 dropped.
38 Instances of class _Feature have two corresponding methods,
39 .getOptionalRelease() and .getMandatoryRelease().
41 CompilerFlag is the (bitfield) flag that should be passed in the fourth
42 argument to the builtin function compile() to enable the feature in
43 dynamically compiled code. This flag is stored in the .compiler_flag
44 attribute on _Future instances. These values must match the appropriate
45 #defines of CO_xxx flags in Include/compile.h.
47 No feature line is ever to be deleted from this file.
48 """
50 all_feature_names = [
51 "nested_scopes",
52 "generators",
53 "division",
56 __all__ = ["all_feature_names"] + all_feature_names
58 # The CO_xxx symbols are defined here under the same names used by
59 # compile.h, so that an editor search will find them here. However,
60 # they're not exported in __all__, because they don't really belong to
61 # this module.
62 CO_NESTED = 0x0010 # nested_scopes
63 CO_GENERATOR_ALLOWED = 0x1000 # generators
64 CO_FUTURE_DIVISION = 0x2000 # division
66 class _Feature:
67 def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
68 self.optional = optionalRelease
69 self.mandatory = mandatoryRelease
70 self.compiler_flag = compiler_flag
72 def getOptionalRelease(self):
73 """Return first release in which this feature was recognized.
75 This is a 5-tuple, of the same form as sys.version_info.
76 """
78 return self.optional
80 def getMandatoryRelease(self):
81 """Return release in which this feature will become mandatory.
83 This is a 5-tuple, of the same form as sys.version_info, or, if
84 the feature was dropped, is None.
85 """
87 return self.mandatory
89 def __repr__(self):
90 return "_Feature" + repr((self.optional,
91 self.mandatory,
92 self.compiler_flag))
94 nested_scopes = _Feature((2, 1, 0, "beta", 1),
95 (2, 2, 0, "alpha", 0),
96 CO_NESTED)
98 generators = _Feature((2, 2, 0, "alpha", 1),
99 (2, 3, 0, "final", 0),
100 CO_GENERATOR_ALLOWED)
102 division = _Feature((2, 2, 0, "alpha", 2),
103 (3, 0, 0, "alpha", 0),
104 CO_FUTURE_DIVISION)