On 9/13/2018 8:04 PM, Victor Stinner wrote:
Le ven. 14 sept. 2018 à 00:09, Eric V. Smith <e...@trueblade.com> a écrit :
f'{type(obj)}' becomes type(obj).__format__(''), so you can return
something other than __str__ or __repr__ does. It's only by convention
that an object's __format__ returns __str__: it need not do so.
What's New in Python 3.7 contains:
object.__format__(x, '') is now equivalent to str(x) rather than
format(str(self), '').
(Contributed by Serhiy Storchaka in bpo-28974.)
https://bugs.python.org/issue28974
Oh, I didn't know that a type is free to change this behavior: return
something different than str(obj) if the format spec is an empty
string.
True! That issue was specific to object.__format__, not any other
classes implementation of __format__.
So are you suggesting to change type(obj).__format__('') to return the
fully qualified name instead of repr(type)?
I'm not suggesting it, I'm saying it's possible. It indeed might be the
most useful behavior.
So "%s" % type(obj) would use repr(), but "{}".format(type(obj)) and
f"{type(obj)}" would return the fully qualified name?
"%s" % type(obj) would use str(), not repr.
You could either:
- keep with convention and have type(obj).__format__('') return
type(obj).__str__(), while type(obj).__format__('#') (or what other char you
want to use) return the qualname;
or
- just have type(obj).__format__('') return the qualname, if that's the more
useful behavior.
Eric
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