On Mon, Nov 8, 2021 at 1:43 PM Ethan Furman <et...@stoneleaf.us> wrote:
> When is an empty container contained by a non-empty container?
>
> For example:
>
> {} in {1:'a', 'b':2} <-- TypeError because of hashability
>
(You accidentally wrote a square close bracket, but I know you meant a
curly close brace. :-}
> set() in {1, 2, 'a', 'b'} <-- ditto
>
> [] in ['a', 'b', 1, 2] <-- False
>
These examples make me think that you're somehow confused between "is an
element of" (which for Python sets is spelled using 'in', and has a similar
spelling and meaning for dicts and sequences), and "is a subset of" (which
we spell as '<=' for sets, and don't support for other types).
> '' in 'a1b2' <-- True
>
As Steven explained this is a different case again (subsequence, not subset
or element).
SomeFlag.nothing in SomeFlag.something <-- ???
>
This case definitely sounds to me like there is that confusion. Assuming
'nothing' is zero, it is not an *element*, so it should not be tested with
'in'. The 'in' operator should only be used if the left operator represents
exactly one flag set.
--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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