Bytes iterator to file object

iterio.py

import io
import itertools


class IteratorIO(io.RawIOBase):
    def __init__(self, iterator: [bytes]):
        super(IteratorIO, self).__init__()
        self.iterator = iterator

    def read(self, n: int = -1) -> bytes:
        if n == -1:
            return b''.join(self.iterator)

        data = b''
        i = n

        while i > 0:
            try:
                chunk = next(self.iterator)
                i -= len(chunk)
                data += chunk
            except StopIteration:
                return data

        last = data[:n]
        data = data[i:]

        self.iterator = itertools.chain([data], self.iterator)

        return last

# Usage
i = (i for i in (b'1234567890', b'abcdefghij'))
i = IteratorIO(i)
assert i.read(12) == b'1234567890ab'
assert i.read(1) == b'c'
assert i.read(2) == b'de'
assert i.read(10) == b'fghij'
assert i.read(5) == b''