[Python-Dev] format, int, and IntEnum

Ethan Furman ethan at stoneleaf.us
Wed Aug 21 09:06:13 CEST 2013

On 08/20/2013 11:15 PM, Ethan Furman wrote:
> On 08/14/2013 09:27 PM, Nick Coghlan wrote:
>> For enums, I believe they should be formatted like their
>> base types (so !s and !r will show the enum name, anything without
>> coercion will show the value) .
> I agree.  While one of the big reasons for an Enum type was the pretty
> str and repr, I don't see format in that area.
> How often will one type in `"{}".format(some_var)` to find out what type
> of object one has?  Myself, I would just type `some_var`.

So, these are some of the ways we have to display an object:

str()       calls obj.__str__()
repr()      calls obj.__repr__()

"%s"        calls obj.__str__()
"%r"        calls obj.__repr__()
"%d"        calls... not sure, but we see the int value

"{}".format()  should (IMO) also display the value of the object

Using int as the case study, its presentation types are ['b', 'd', 'n', 
'o', 'x', 'X'].  Notice there is no 's' nor 'r' in there, as int expects 
to display a number, not arbitrary text.

So, for mixed-type Enumerations, I think any format calls should simply 
be forwarded to the mixed-in type (unless, of course, a custom 
__format__ was specified in the new Enumeration).


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