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[Python-Dev] When should pathlib stop being provisional?

Nick Coghlan ncoghlan at gmail.com
Wed Apr 6 00:49:33 EDT 2016 
On 6 April 2016 at 13:06, Alexander Walters <tritium-list at sdamon.com> wrote:
> I think the naysayers would be satisfied with an object that... while not
> str or bytes or a derived class of either... acted like str when it had to.
> Is that possible without deriving from str or bytes?

Only if the consuming code explicitly casts with "str()", and that's
*too* permissive for most use cases (since __str__ and the __repr__
fallback are completely inappropriate as a "convert to a text
representation of a filesystem path" command).

A "__text__" protocol for non-lossy conversions to str would arguably
be feasible, but its scope goes way beyond what's needed for a "rich
path object" conversion protocol.

Implementing that model in the general case would require something
more akin to https://www.python.org/dev/peps/pep-0357/, which added
__index__ as a guaranteed-non-lossy conversion from other types to a
builtin integer, allowing non-builtin integers to accepted for things
like slicing and sequence repetition, without inadvertently also
accepting non-integral types like builtin floats.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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