New submission from Dan Snider <[email protected]>:
ie.:
>>> from struct import calcsize
>>> calcsize('\144\u0064\000xf\U00000031000\60d\121\U00000051')
16
I'm sure some people think it's obvious or even expect the null character to
signal EOF but it probably isn't obvious at all to those without experience in
lower level languages. It actually seems like Python goes out of its way to
make sure everything treats the null character no more special than the letter
"H", which is good.
At first glance I'd think something like this was just another trivial quirk of
the language and not bring it up, but because the documentation doesn't mention
it I actually got stuck on something related for half an hour when unit testing
some dynamically generated format specs.
Without going into unnecessary detail, what happened was that a typo in another
tangentially related part of the test was enabling the generation of a rogue
null byte. I'm bad at those "find face in the crowd" puzzles and this was
hardly different, being literally camouflaged within a 300 character format
spec containing a random mixture of escaped and non-escaped source characters
in the forms: \Uffffffff, \uffff, \777, \xff, \x00, + latin/ascii.
If I'm not the only one who sees this as a slightly bigger deal than poor
documentation, the fix is trivial with an extra call to PyBytes_GET_SIZE when
null is found. But just because I can't think of a use case in allowing the
null character to precede other characters in the format string doesn't mean
there isn't one, which is why only documentation is currently selected.
----------
assignee: docs@python
components: Documentation, Library (Lib)
messages: 333424
nosy: bup, docs@python
priority: normal
severity: normal
status: open
title: Document that the null character '\0' terminates a struct format spec
versions: Python 3.6, Python 3.7, Python 3.8
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<https://bugs.python.org/issue35714>
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