On Tue, Apr 20, 2021 at 11:12 AM Ethan Furman <ethan@stoneleaf.us> wrote:
On 4/20/21 8:46 AM, Guido van Rossum wrote:
I'd guess it is totally up to the object, since str() calls `__str__` and format() calls `__format__`. Of course this now begs the question whether those enums should perhaps change their `__format__` to match their `__str__`...?
When Enum was designed we made sure and captured `__repr__` and `__str__`, but not `__format__`. So at this point, `__format__` is the mixed-in data type's -- so `int.__format__` in the case of IntEnum. However, if a user updates the `__str__` of their Enum, then that will be used in the format:
```python from enum import IntEnum
class Color(IntEnum): RED = 1
format(Color.RED) # '1'
class Color(IntEnum): RED = 1 def __str__(self): return 'one'
format(Color.RED) # 'one' ```
But that would not suit your purpose. Then again, how would one get the pretty IntEnum-specific representation in a format- or f-string? I guess f"{flag!s}" would work.
Yup, that does work.
There is at least one user who is depending on `format()` using `int.__format__` because they filed a bug report when I broke it.
Moving forward, I'm not sure having format() and str() ever be different is a good idea, especially since users who need, for example, Color.RED to be '1' can simply add a `__str__ = int.__str__` to their own custom base IntEnum class and be good to go. If we deprecate the current behavior now we could change it in 3.12.
Thoughts?
So to be clear, that one user wants f"{Color.RED}" to return "1" and not " Color.RED" (or something like that). And you want f"{Color.RED}" and str(Color.RED) to return the same value. Then together that means that str(Color.RED) must also return "1". Did I get that right? And are you happy with that outcome? -- --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-c...>