In the Python 3.10 Doc/library/enum.rst file was the following:
.. class:: FlagBoundary
*FlagBoundary* controls how out-of-range values are handled in *Flag* and its
subclasses.
.. attribute:: STRICT
Out-of-range values cause a :exc:`ValueError` to be raised. This is the
default for :class:`Flag`::
>>> from enum import STRICT
>>> class StrictFlag(Flag, boundary=STRICT):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
>>> StrictFlag(2**2 + 2**4)
Traceback (most recent call last):
...
ValueError: StrictFlag: invalid value: 20
given 0b0 10100
allowed 0b0 00111
.. attribute:: CONFORM
Out-of-range values have invalid values removed, leaving a valid *Flag*
value::
>>> from enum import CONFORM
>>> class ConformFlag(Flag, boundary=CONFORM):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
>>> ConformFlag(2**2 + 2**4)
ConformFlag.BLUE
.. attribute:: EJECT
Out-of-range values lose their *Flag* membership and revert to :class:`int`.
This is the default for :class:`IntFlag`::
>>> from enum import EJECT
>>> class EjectFlag(Flag, boundary=EJECT):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
>>> EjectFlag(2**2 + 2**4)
20
.. attribute:: KEEP
Out-of-range values are kept, and the *Flag* membership is kept. This is
used for some stdlib flags:
>>> from enum import KEEP
>>> class KeepFlag(Flag, boundary=KEEP):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
>>> KeepFlag(2**2 + 2**4)
KeepFlag.BLUE|0x10
All four tests are relying on a previous `from enum import Flag`, but only the three tests pass -- the fourth raises:
Traceback (most recent call last):
File "/home/runner/work/cpython/cpython/Lib/doctest.py", line 1337, in __run
exec(compile(example.source, filename, "single",
File "<doctest default[1]>", line 1, in <module>
class KeepFlag(Flag, boundary=KEEP):
NameError: name 'Flag' is not defined
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