Ability to specify function for auto-test in Enum and pass the given value as an argument to _generate_next_value_
After messing around with `Enum` for a while, there's one small thing that I'd like to see improved. It seems limiting to me that the only way to trigger `_generate_next_value` is to pass `auto()`. What if, for a particular `Enum`, I would like to be able to use `()` as a shorthand for `auto()`? How about a more complex auto-generation that determines the final value based on both the given value and the name/key As an example of the second case, start with an `Enum` subclas in which each item, by default, has the name/key as its value and a prettified version of the name as its label, but one can also specify the value and label using a 2-item tuple for the value. Now, let's say we want to be able to specify a custom label and still use the name/key as the value either as a None/label tuple or as a string starting with a comma. Using a custom test for auto, one could identify those cases, Passing the assigned value to the `_generate_next_value_` function would allow it to make use of that information. For backward compatibility, the signature of the `_generate_next_value_` function can be checked to make sure it can accept the extra argument for that before passing that.
Steve Jorgensen wrote:
What's wrong with `auto()`? Why do you need a shorthand for that? Also `()` is an empty tuple so it's just another enum value.
It seems that your second case can be accomplished by using a custom descriptor that receives the field name via `__set_name__`. For example: from enum import Enum class Value: def __init__(self, val): self.val = val self.name = None def __set_name__(self, owner, name): self.name = name def __get__(self, instance, owner=None): return f'{self.name} {self.val}' def __set__(self, instance, value): raise AttributeError class MyEnum(Enum): RED = Value(1) GREEN = Value(2) BLUE = Value(3)
I repeatedly make proposals without examples. Sorry about that, and I'm going to stop doing that. Upon trying to compose an example, I realize that what I'm asking for is not actually the best pattern for what I'd like to see, so when I have composed a better pattern and sample implementation, I'll post a new request.
Steve Jorgensen wrote:
See new request at https://mail.python.org/archives/list/python-ideas@python.org/thread/INFWIWT...
Steve Jorgensen wrote:
What's wrong with `auto()`? Why do you need a shorthand for that? Also `()` is an empty tuple so it's just another enum value.
It seems that your second case can be accomplished by using a custom descriptor that receives the field name via `__set_name__`. For example: from enum import Enum class Value: def __init__(self, val): self.val = val self.name = None def __set_name__(self, owner, name): self.name = name def __get__(self, instance, owner=None): return f'{self.name} {self.val}' def __set__(self, instance, value): raise AttributeError class MyEnum(Enum): RED = Value(1) GREEN = Value(2) BLUE = Value(3)
I repeatedly make proposals without examples. Sorry about that, and I'm going to stop doing that. Upon trying to compose an example, I realize that what I'm asking for is not actually the best pattern for what I'd like to see, so when I have composed a better pattern and sample implementation, I'll post a new request.
Steve Jorgensen wrote:
See new request at https://mail.python.org/archives/list/python-ideas@python.org/thread/INFWIWT...
participants (4)
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Anders Hovmöller -
Antoine Rozo -
Dominik Vilsmeier -
Steve Jorgensen