On 7 May 2018 at 12:35, Chris Angelico <rosuav@gmail.com> wrote:

On Mon, May 7, 2018 at 12:13 PM, Nick Coghlan <ncoghlan@gmail.com> wrote:
> So I have a different suggestion: perhaps it might make sense to propose
> promoting a key handful of path manipulation operations to the status of
> being builtins?
>
> Specifically, the ones I'd have in mind would be:
>
> - dirname (aka os.path.dirname)
> - joinpath (aka os.path.join)

These two are the basics of path manipulation. +1 for promoting to
builtins, unless pathlib becomes core (which I suspect isn't
happening).

pathlib has too many dependencies to ever make the type available as a builtin:

    $ ./python -X importtime -c pass 2>&1 | wc -l
    25
    $ ./python -X importtime -c "import pathlib" 2>&1 | wc -l
    53

It's a good way of unifying otherwise scattered standard library APIs, but it's overkill if all you want to do is to calculate and resolve some relative paths.

> - abspath (aka os.path.abspath)

Only +0.5 on this, as it has to do file system operations. It may be
worthwhile, instead, to promote os.path.normpath, which (like the
others) is purely processing the string form of the path. It'll return
the same value regardless of the file system.

My rationale for suggesting abspath() over any of its component parts is based on a few key considerations:

- "make the given path absolute" is a far more common path manipulation activitity than "normalise the given path" (most users wouldn't even know what the latter means - the only reason *I* know what it means is because I looked up the docs for abspath while writing my previous comment)

- __file__ isn't always absolute (especially in __main__), so you need to be able to do abspath(__file__) in order to reliably apply dirname() more than once
- it can stand in for both os.getcwd() (when applied to the empty string or os.curdir) and os.path.normpath() (when the given path is already absolute), so we get 3 new bits of builtin functionality for the price of one new builtin name

- I don't want to read "normpath(joinpath(getcwd(), relpath))" when I could be reading "abspath(relpath)" instead

Cheers,

Nick.

Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia