On Sat, 12 Feb 2022 at 09:34, Ricky Teachey <ri...@teachey.org> wrote:
>
> On Fri, Feb 11, 2022 at 4:58 PM MRAB <pyt...@mrabarnett.plus.com> wrote:
>>
>> On 2022-02-11 20:05, Ricky Teachey wrote:
>> > Just had a thought kernel: what if there were an f-string mini-language
>> > directive to grab environment variables and expand user paths? That
>> > seems to me like it could be even more useful beyond just working with
>> > paths.
>> >
>> > Maybe something like:
>> >
>> > f"{my_var:$}"
>> >
>> > This would return the same as os.path.expandvars("$my_var")
>> >
>> No, that would be the value of the Python variable 'my_var' with the
>> format string "$".
>
>
> well right now $ is not a valid format string for f-strings. what i'm
> suggesting is to add $ to the format spec mini-languagem and have the result
> be an expanded environment variable value.
>
> but you're right, i guess it would apply this to the contents of the variable
> my_var, not the STRING my_var. so maybe the spelling would need to use a
> nested quotation, like this:
>
> f"{'my_var':$}"
>
> this would be the same as os.path.expandvars("$my_var")
>
Why shoehorn it into f-strings? Even worse: Why should f-strings fetch
external information in such a hidden way?
One thing I'm not fully aware of here is what precisely is wrong with
the status quo. Are you looking for a method instead of a function? Do
you need something that takes a Path and returns a Path? The existing
os.path.expandvars will happily accept a Path and return a str:
>>> import pathlib, os.path
>>> pathlib.Path("$HOME/cpython/Grammar/python.gram")
PosixPath('$HOME/cpython/Grammar/python.gram')
>>> os.path.expandvars(pathlib.Path("$HOME/cpython/Grammar/python.gram"))
'/home/rosuav/cpython/Grammar/python.gram'
>>> type(_)
<class 'str'>
I'm confused, since anything involving f-strings clearly has nothing
to do with pathlib (other than in the trivial sense that you could
expand vars before constructing a Path), but the OP was very
definitely talking about Path objects.
ChrisA
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