Is it possible something like lvalue of perl or setf of lisp in python?

Question

In lisp you can say:

(setf (aref a 1) 5)

In perl you can say:

substr( $string, $start, $stop ) =~ s/a/b/g

Answer 1

In short, no.

However, if you define __setitem__, you can assign to a subscript, e.g.

foo['subscript'] = 7

And you could return foo (and also the subscript, if you wanted) from a function.

container, subscript = whatevs()
container[subscript] = 7

or, in one line:

operator.setitem(*(whatevs()+(7,)))

See operator.