>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
This will probably be TIL for many people. It is a surprisingly hidden feature.
I for one, still like the "%s" % x instead of "{0}".format(x). It is simply shorter and I already know or use printf for C in other parts of the project. But with the new f"..." interpolation, I can see liking that more. I am all for being as concise as possible while still being explicit (if that makes any sense at all ;-) ).
I've always found templates way overkill for most of my needs, but they cover a specific and legitimate use-case (large and complex blocks of text).
In the same way, .format() solved the problem of inconsistency and bugs happening all the time with %. It was a restriction and formalization effort, trying to root out bad practices and hence slightly more explicit, but it made sense.
The new f'' IMHO does not solve anything beyond pandering to developer laziness. It will likely introduce bugs in places where developers are not clear about the context ("oh, I thought we didn't have a 'x' var at this point, turns out we do!"), because (from what I understand) it takes away the ability to define which variables should be considered.
Luckily it will take a while before it percolates in any significant library, but I sincerely hope it just doesn't gain much traction.
