On 5/9/18 10:01 AM, Paul Moore wrote:
On 9 May 2018 at 14:49, Eric V. Smith <e...@trueblade.com> wrote:
I would object to changing the format machinery. Any format spec should be
interpreted by some object's __format__ method.
Agreed. In theory this is a nice idea, but the way formatting is
implemented (and the fact that join is a method on strings taking an
arbitrary iterable as an argument) means that it's a bad fit for the
format mini-language.
I don't think the improved convenience is sufficient to warrant the
change that would be required in practice. (But if someone found a way
to make it work *without* changes to the underlying format machinery,
that would be a different matter...)
Well, since you asked, let's combine this with dataclasses, because we can!
from dataclasses import dataclass
from typing import List
@dataclass
class Join:
o: List[str] # or similar
def __format__(self, spec):
return spec.join(self.o)
l = ['a', 'b']
print('{:, }'.format(Join(l)))
print(f'{Join(l):-}')
Gives:
a, b
a-b
Eric
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