Steven D'Aprano wrote:
On Tue, Mar 24, 2020 at 08:14:33PM -0000, Dennis Sweeney wrote:
I think then maybe it would be preferred to use the something like the following in the PEP: def cutprefix(self, prefix, /): if isinstance(prefix, str): if self.startswith(prefix): return self[len(prefix):] return self[:]
Didn't we have a discussion about not mandating a copy when nothing changes? For strings, I'd just return self. It is only bytearray that requires a copy to be made.
It appears that in CPython, ``self[:] is self`` is true for base ``str`` objects, so I think ``return self[:]`` is consistent with (1) the premise that returning self is an implementation detail that is neither mandated nor forbidden, and (2) the premise that the methods should return base ``str`` objects even when called on ``str`` subclasses.
elif isinstance(prefix, tuple): for option in prefix: if self.startswith(option): return self[len(option):]
I'd also remove the entire multiple substrings feature, for reasons I've
already given. "Compatibility with startswith" is not a good reason to add this feature and you haven't established any good use-cases for it. A closer analog is str.replace(substring, ''), and after almost 30 years of real-world experience, that method still only takes a single substring, not a tuple.
The ``test_concurrent_futures.py`` example seemed to be a good use case to me. I agree that it would be good to see how common that actually is though. But it seems to me that any alternative behavior, e.g. repeated removal, could be implemented by a user on top of the remove-only-the-first-found behavior or by fluently chaining multiple method calls. Maybe you're right that it's too complex, but I think it's at least worth discussing.