[Python-ideas] IntFlags

[Ethan Furman]

On 03/07/2015 02:50 AM, Serhiy Storchaka wrote:
> On 07.03.15 10:07, Ethan Furman wrote:
>> On 03/03/2015 07:52 AM, Serhiy Storchaka wrote:
>>
>>> We need new type IntFlags. It is like IntEnum, but has differences:
>>>
>>> 1. The value of an instance should be not limited to the set of predefined constants. It can be a combination of
>>> predefined constants or even arbitrary integer.
>>>
>>> 2. The result of "|", "&" and "~" operators for IntFlags arguments should be an instance of the same IntFlags subclass.
>>>
>>> 3. It should have nice str() and repr().
>>
>> As long as we are dreaming  :)
>>
>> class Stat(IntFlag):
>>      RDONLY = 1
>>      NOSUID = 2
>>      NODEV = 4
>>      NOEXEC = 8
>>      SYNCHRONOUS = 16
>>      MANDLOCK = 64
>>      WRITE = 128
>>      APPEND = 256
>>      NOATIME = 1024
>>      NODIRATIME = 2048
>>      RELATIME = 4096
>>
>> a = Stat.RDONLY  # creates a new instance of Stat, not a singleton
> 
> IntFlags is purposed to replace existing integer constants (as IntEnum).
> 
> globals().update(Stat.__members__)

And that can still work -- if the flag is accessed from the class (Stat.RDONLY) it will always be the value assigned
(1); if it is accessed from a member, it will be the value assigned /if set/, otherwise 0.

This also has the advantage of supporting both C style operations (x = Stat.WRITE | Stat.APPEND), or the more customary
Python operations (x = Stat.WRITE; x.APPEND = True).

--
~Ethan~

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