you can already put an arbitrary expression in a f-string -- that's the
point. So what's wrong with:
In [12]: eget = os.environ.get
In [13]: f"{eget('HOME')}/bin"
Out[13]: '/Users/chris/bin'
This seems a rare enough need that special built-in support is not worth it.
-CHB
On Fri, Feb 11, 2022 at 6:01 PM Eric V. Smith <e...@trueblade.com> wrote:
> On 2/11/2022 5:33 PM, Ricky Teachey 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.
>
> Off topic: there are no characters that are invalid format strings, except
> '!' and ':'. For example, datetime allows anything, since it's passed on to
> strftime:
>
> >>> from datetime import date
> >>> f'{datetime.now():This is a test $@$&*()}'
> 'This is a test $@$&*()'
>
> Or:
>
> >>> class F:
> ... def __format__(self, fmt):
> ... if fmt == '$':
> ... return 'dollar'
> ... return 'something else'
> ...
> >>> f'{F():$}'
> 'dollar'
> >>> f'{F():x}'
> 'something else'
>
> Eric
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--
Christopher Barker, PhD (Chris)
Python Language Consulting
- Teaching
- Scientific Software Development
- Desktop GUI and Web Development
- wxPython, numpy, scipy, Cython
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