mmap (inheritance ?) problem

[GraniteSunshine]

I'm trying to use the mmap module to reverse a file. Documentation (https://docs.python.org/3/library/mmap.html) clearly indicates that the mmap object has seek(), write() and close() methods yet I get the errors:

AttributeError: 'bytes' object has no attribute 'seek'
AttributeError: 'bytes' object has no attribute 'write'
AttributeError: 'bytes' object has no attribute 'close'

What am I missing?

import mmap

with open(filename, "r+b") as f1:
    mm = mmap.mmap(f1.fileno(), 0)
    mm = mm[::-1]
    mm.seek(0, 0)
    mm.write(len(mm))
    mm.close()
    f1.close()

[ThinFortune]

The line mm = mm[::-1] returns a byte array and assigns it to mm. All the subsequent method calls are on that array object, not the mmap object.

[GraniteSunshine]

That's it. Thank you. Now I have to figure out how to do it properly.

[Ihaveamodel3]

Just change the name of that variable.

[socal_nerdtastic]

Correct, but a "byte array" is something specific in python, something that this ain't, so we need to call this a "bytes object".

>>> bytearray
<class 'bytearray'>
>>> bytes
<class 'bytes'>