[New-bugs-announce] [issue26358] mmap.mmap.__iter__ is broken (yields bytes instead of ints)

Antti Haapala report at bugs.python.org
Sat Feb 13 22:37:46 EST 2016

New submission from Antti Haapala:

Just noticed when answering a question on StackOverflow (http://stackoverflow.com/q/35387843/918959) that on Python 3 iterating over a mmap object yields individual bytes as bytes objects, even though iterating over slices, indexing and so on gives ints


    import mmap

    with open('test.dat', 'rb') as f:
        mm = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
        for b in mm:
            # prints for example b'A' instead of 65

I believe this should be fixed for the sake of completeness - the documentation says that "Memory-mapped file objects behave like both bytearray and like file objects." - however the current behaviour is neither like a bytearray nor like a file object, and quite confusing.

Similarly the `in` operator seems to be broken; one could search for space using `32 in bytesobj`, which would work for slices but not for the whole mmap object.

messages: 260261
nosy: ztane
priority: normal
severity: normal
status: open
title: mmap.mmap.__iter__ is broken (yields bytes instead of ints)
type: behavior
versions: Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6

Python tracker <report at bugs.python.org>

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