[issue32349] Add detailed return value information for set.intersection function
New submission from 양유석 <ileixe@gmail.com>: I think it's intentional behavior seems to be minor though. At a glance, I assume that a.set(b) should return items in a. But I found out the implementation always return items in smaller set. There is no issue for common case, but custom class can make a trouble. So, I think additional information of return value is helpful. ---------- assignee: docs@python components: Documentation messages: 308484 nosy: docs@python, 양유석 priority: normal severity: normal status: open title: Add detailed return value information for set.intersection function type: enhancement _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue32349> _______________________________________
Mark Dickinson <dickinsm@gmail.com> added the comment: To clarify, are you referring to this behaviour?
a = {1, 2, 3} b = {1.0, 4.0} a.intersection(b) # expect {1} {1.0}
I'd personally expect this to be implementation-dependent: since for set operations you usually only care about objects up to equality, it would be a bit unusual to care whether you get {1} or {1.0} in the above situation, and I'd say the implementation should be free to do whatever's convenient. Making documented guarantees would unnecessarily constrain other implementations. I suppose one could document the *lack* of a guarantee here ... ---------- nosy: +mark.dickinson, rhettinger _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue32349> _______________________________________
Raymond Hettinger <raymond.hettinger@gmail.com> added the comment: The implementation detail is not documented because it is not guaranteed. The behavior has changed over time and other implementation are allowed to do something different. For example, collections.abc.Set.__and__ has different behavior. ---------- resolution: -> not a bug stage: -> resolved status: open -> closed _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue32349> _______________________________________
양유석 <ileixe@gmail.com> added the comment: Ok, I got a point of implementation-dependent things. Thank you for comments. ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue32349> _______________________________________
participants (3)
-
Mark Dickinson -
Raymond Hettinger
-
양유석