New submission from Arthur Darcet: If I'm not mistaken, a BytesIO buffer can be in three states:
(1) `b = BytesIO(b'data')` -> free of any constraints (2) `d = b'data'; b = BytesIO(d)` -> cannot modify the underlying bytes without copying them (3) `b = BytesIO(b'data'); d = b.getbuffer()` -> cannot return a "bytes" representation of the data without copying it (the underlying buffer might change) My use-case is "how to get the length of the data currently in the BytesIO object". And right now, there are two solutions: (a) `len(b.getvalue())` (b) `len(b.getbuffer())` but, solution (a) is copying data if the buffer is in state (3) ; and solution (b) is copying data for state (2). And I don't see any way to distinguish between the three states from Python code. So as far as I understand it, there is no way to get the size of the buffer in Python that would reliably not copy any data Should I open a PR to add a `size()` method on the BytesIO class? (simply returning `PyLong_FromSsize_t(self->string_size)` ---------- components: IO messages: 299054 nosy: rthr priority: normal severity: normal status: open title: io.BytesIO: no way to get the length of the underlying buffer without copying data type: enhancement versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue31025> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
