[Python-ideas] Pass a function as the argument "step" of range()

[Chris Angelico]

On Fri, Jul 3, 2015 at 5:30 PM, Pierre Quentel <pierre.quentel at gmail.com> wrote:
> With the proposed Range class, here is an implementation of the Fibonacci
> sequence, limited to 2000 :
>
> previous = 0
> def fibo(last):
>     global previous
>     _next, previous = previous+last, last
>     return _next
>
> print(list(Range(1, 2000, fibo)))

Without the proposed Range class, here's an equivalent that doesn't
use global state:

def fibo(top):
    a, b = 0, 1
    while a < 2000:
        yield a
        a, b = a + b, a

print(list(fibo(2000)))

I'm not seeing this as an argument for a variable-step range
func/class, especially since you need to use a global - or to
construct a dedicated callable whose sole purpose is to maintain one
integer of state. Generators are extremely expressive and flexible.

ChrisA