On Wed, Mar 17, 2021, 5:34 AM Serhiy Storchaka <storch...@gmail.com> wrote:
> 12.03.21 23:48, Ethan Furman пише: > > A question that comes up quite a bit on Stackoverflow is how to test to > > see if a value will result in an Enum member, preferably without having > > to go through the whole try/except machinery. > > > ... > > Thoughts? > > The Enum class is already too overloaded. I sometimes think about adding > SimpleEnum class with minimal simple functionality which would allow to > use enums in more modules sensitive to import time. > > As for solving your problem, try/except looks the best solution to me. > > try: > Color(1) > except ValueError: > ... # invalid color > else: > ... # valid color > > If you don't like try/except, the second best solution is to add a > module level helper in the enum module: > > def find_by_value(cls, value, default=None): > try: > return cls(value) > except ValueError: > return default > > You can add also find_all_by_value(), get_aliases(), etc. It is > important that they are module-level function, so they do not spoil the > namespace of the Enum class. > +1 on a module level helper. The preponderance of stackoverflow questions seem convincing enough that people want to do this and it seems like a reasonable request. And I have wanted to do something like this myself, so I'd probably use it. I see it as analogous to situations when you want to use dict.get(key) instead of dict[key]. But adding a non-dunder method to the Enum class namespace seems more suboptimal to me compared to a module level helper, because of the namespace spoiling/crowding issue. No matter what method name were to be chosen, someone at some point would want to use it as an Enum member name (unless of course it's a reserved dunder method).
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