[Python-ideas] Draft PEP on string interpolation

[Nikolaus Rath]

On Aug 23 2015, Nick Coghlan <ncoghlan-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> On 23 August 2015 at 11:37, Nick Coghlan <ncoghlan-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
>> However, I'm now coming full circle back to the idea of making this a
>> string prefix, so that would instead look like:
>>
>>     subprocess.call($"echo $filename")
>>
>> The trick would be to make interpolation lazy *by default* (preserving
>> the triple of the raw template string, the parsed fields, and the
>> expression values), and put the default rendering in the resulting
>> object's *__str__* method.
>
> Indeed, after working through this latest change, I ended up back
> where I started from a syntactic perspective, with a proposal for
> i(nterpolated)-strings rather than f(ormatted)-strings:
> https://www.python.org/dev/peps/pep-0501/
>
> With appropriate modifications to subprocess.call, the proposal would
> then enable us to write a *safe* shell command interpolation as:
>
>     subprocess.call(i"echo $filename")

I like the idea, but *please* stop using this example. It's just
terrible. Firstly, subprocess.call defaults to shell=False, so this
wouldn't even work. Secondly, subprocess.call('echo', filename') looks
orders of magnitude cleaner. Thirdly, your i-string wouldn't even know
how to quote because it doesn't know what shell you are using.


Best,
-Nikolaus

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