Python mmap.mmap() to bytes-like object?

The documentation for mmap says that "Memory-mapped file objects behave like both bytearray and like file objects."

However, that doesn't seem to extend to a standard for loop: At least for Python 3.8.5 on Linux which I'm currently using, each mmap.mmap() iterator element is a single-byte bytes, while for both a bytearray and for normal file access each element is an int instead. Update. Correction: For normal file access it is a variable-sized bytes; see below.

Why is that? And more importantly, how can I efficiently get a bytes-like object from an mmap, so one where not only indexing but also for gives me an int? (By efficiently, I mean that I'd like to avoid additional copying, casting, etc.)

Here is code to demonstrate the behavior:

#!/usr/bin/env python3.8

def print_types(desc, x):
    for el in setmm: break   ### UPDATE: bug here, `setmm` should be `x`, see comments
    # `el` is now the first element of `x`
    print('%-30s: type is %-30s, first element is %s' % (desc,type(x),type(el)))
    try: print('%72s(first element size is %d)' % (' ', len(el)))
    except: pass # ignore failure if `el` doesn't support `len()`

setmm = bytearray(b'hoi!')
print_types('bytearray', setmm)

with open('set.mm', 'rb') as f:
    print_types('file object', f)

with open('set.mm', 'rb') as f:
    setmm = f.read()
    print_types('file open().read() result', setmm)

import mmap
with open('set.mm', 'rb') as f:
    setmm = mmap.mmap(f.fileno(), 0, prot=mmap.PROT_READ)
    print_types('file mmap.mmap() result', setmm)

which results in

bytearray                     : type is <class 'bytearray'>           , first element type is <class 'int'>
file object                   : type is <class '_io.BufferedReader'>  , first element type is <class 'int'>
file open().read() result     : type is <class 'bytes'>               , first element type is <class 'int'>
file mmap.mmap() result       : type is <class 'mmap.mmap'>           , first element type is <class 'bytes'>
                                                                        (first element size is 1)

Update. With the bug fixed that furas kindly pointed out in the comments, the result becomes

bytearray                     : type is <class 'bytearray'>           , first element is <class 'int'>
file object                   : type is <class '_io.BufferedReader'>  , first element is <class 'bytes'>
                                                                        (first element size is 38)
file open().read() result     : type is <class 'bytes'>               , first element is <class 'int'>
file mmap.mmap() result       : type is <class 'mmap.mmap'>           , first element is <class 'bytes'>
                                                                        (first element size is 1)

Which answers what happens: For some reason iterating over an mmap is like iterating over a file, returning a bytes every time, but not with full lines like for a file, but single-byte chunks.

Still my main question is unchanged: How can I efficiently have an mmap behave like a bytes-like object (i.e., both indexing and for give int)?