Python 3.6 is getting literal string interpolation (see PEP 498). This is an imperfect backport for older Python versions.

>>> from f_strings import f
>>> adjective = 'great'
>>> f('f-strings are {adjective}!')
'f-strings are great!'

• Uses globals and locals, so cannot access variables from closures (see https://www.python.org/dev/peps/pep-0498/#no-use-of-globals-or-locals)
• Uses the existing string format parser, so expressions cannot contain {, } or !.