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bpo-32218: make Flag
and IntFlag
members iterable
#22221
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Original file line number | Diff line number | Diff line change |
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@@ -728,6 +728,10 @@ def __contains__(self, other): | |
type(other).__qualname__, self.__class__.__qualname__)) | ||
return other._value_ & self._value_ == other._value_ | ||
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def __iter__(self): | ||
members, extra_flags = _decompose(self.__class__, self.value) | ||
return (m for m in members if m._value_ != 0) | ||
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Comment on lines
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to
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. The I can think of two efficient ways:
return (v for v in self.__class__ if v.value != 0 and (v.value & (v.value-1) == 0) and v in self)
@staticmethod
def _bits(n):
while n:
b = n & (~n+1)
yield b
n ^= b
def __iter__(self):
return (self.__class__(v) for v in self._bits(self._value_)) in fact There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. proposal (2) is 2x faster than the implementation in this PR, for an enum with only about 6 values... >>> from enum import Flag, auto
>>> class Foo(Flag):
... NONE = 0
... A = auto()
... B = auto()
... C = auto()
... C2 = C
... AB = A | B
... D = auto()
... E = auto()
... F = auto()
...
>>> x = Foo.A | Foo.B | Foo.D | Foo.F
>>> import timeit
>>> timeit.timeit('list(x)', globals=locals(), number=10000)
0.6332780510000013 proposal (2): >>> timeit.timeit('list(x)', globals=locals(), number=10000)
0.36078684099999236 There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I have become increasingly unhappy with the the multiple calls to There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
I do have ideas on it, and intended to open a separate issue for refactoring Regarding bugs, when it's used by >>> class Foo(Flag):
... A = auto()
... B = auto()
... C = auto()
... BC = B | C
>>> repr(Foo.BC)
'<Foo.BC: 6>'
>>> repr(Foo.A | Foo.BC)
'<Foo.BC|C|B|A: 7>'
Comment on lines
+731
to
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I think the use of
I'd argue that There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I agree that the zero-value flag should not be contained in a non-zero flag, but I have no problem with a compound flag showing up if its bits are present. You are welcome to try and convince me otherwise, but it will take more than "no one wants that behavior". There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Hmm, I just learned that >>> class Foo(Flag):
... NONE = 0
... A = 1
... B = 2
... C = 4
... AB = A | B
>>> Foo.AB in (Foo.AB | Foo.C)
True
>>> (Foo.A|Foo.C) in (Foo.AB | Foo.C)
True If that's the case, then actually it's OK for >>> set().issubset({1, 2})
True I would not have made the API this way. |
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def __repr__(self): | ||
cls = self.__class__ | ||
if self._name_ is not None: | ||
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1 @@ | ||
`enum.Flag` and `enum.IntFlag` members are now iterable |
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The meaning of "members" should be clarified. Specifically, the iteration intentionally omits aliases and compound members.
The tests should verify this.
I would describe it as "iterating over the bits of a flag value", because that's what it does. Using "bits" should be OK since
Flag
is documented as supporting bitwise operators.There was a problem hiding this comment.
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I agree.