[Python-Dev] bpo-34595: How to format a type name?

Victor Stinner vstinner at redhat.com
Thu Sep 13 20:04:53 EDT 2018

Le ven. 14 sept. 2018 à 00:09, Eric V. Smith <eric at 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.)


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

So are you suggesting to change type(obj).__format__('') to return the
fully qualified name instead of repr(type)?

So "%s" % type(obj) would use repr(), but "{}".format(type(obj)) and
f"{type(obj)}" would return the fully qualified name?


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