A silly circular buffer-style map-style iterator

ring.py

#!/usr/bin/env python3

from typing import Iterator
from itertools import cycle, islice, chain

class GetItemIterator(Iterator):
    def __init__(self, *it):
        self._len, it_copy = self._get_len(it)
        self._it = cycle(it_copy)
        self._curr_idx = 0
        self._curr_data = next(self._it)

    @staticmethod
    def _get_len(it):
        len_ = 0
        it_copy = ()
        for i in it:
            it_copy = chain(it_copy, (i,))
            len_ += 1
        return len_, it_copy

    def __getitem__(self, i):
        if i == self._curr_idx:
            return self._curr_data
        elif i > self._curr_idx:
            self._curr_data = next(islice(self._it, i - self._curr_idx))
            self._curr_idx = i
            return self._curr_data
        else:
            # need to roll over
            self._curr_data = next(islice(self,_it, (self._curr_idx + i) % self._len))
            self._curr_idx = (self._curr_idx + i) % self._len
            return self._curr_data

    def __len__(self):
        return self._len

    def __next__(self):
        self._curr_idx = 0 if self._curr_idx - 1 == self._len else self._curr_idx + 1
        return next(self._it)

if __name__ == "__main__":
    it = GetItemIterator(1,2,3, 4)
    for i in range(10):
      print(i, it[i])