[Python-ideas] Draft PEP on string interpolation

[Paul Moore]

On 26 August 2015 at 00:55, Nick Coghlan <ncoghlan at gmail.com> wrote:
> I'm also going to switch to using completely made up API names, since
> folks otherwise anchor on "but that's not the way that API currently
> works" without accounting for the fact that APIs can be updated to
> dispatch to different behaviours based on the types of their arguments
> :)

One advantage of the otherwise unfortunate obsession about "that's not
how os.system works" is that it did flag up in my mind the issue of
backward compatibility, in the form I noted (what if version X of an
API doesn't handle e-strings and so is unsafe, but version X+1 does
handle them and so is safe). Certainly older versions being worse is a
routine issue, but a dependency on what version of a module is
installed very definitely fails your "make the wrong thing easy to
detect" criterion.

One key advantage of the os.system -> subprocess.run migration is that
the wrong thing is easy to detect - if you're using os.system, or
you're not supplying a list, or you have shell=True, you're doing it
wrong.

Your second goal is fairly strongly in conflict with the first one, so
satisfying both of them is the major challenge (I'd personally drop 2
in favour of 1 without a second thought, but I don't have a large
codebase to maintain, so that's an easy choice for me).

Your third goal is fine, but a matter of personal taste. I actually
find subprocess.call([arg, ...]) more readable than
os.system("something or other"). Maybe auto-quoting would change my
mind, but in the first instance I'd probably just think of it as "yet
another quoting syntax whose limitationsI have to remember"

Paul