Package: lexid
lexidlexidis a micro library to increment lexically ordered numerical ids.Throughout the sequence of ids, this expression will always be true, whether you are dealing with integers or strings:older_id < newer_idThe left most character/digit is only used to maintain lexical order, so that the position in the sequence is maintained in the remaining digits.Such ids can be useful as build or version numbers, which are often displayed by tooling which does not understand their correct ordering.Project/Repo:Code Quality/CI:NamerolesinceuntilManuel Barkhau (mbarkhau@gmail.com)author/maintainer2020-09-Usage$ pip install lexid
$ lexid_incr 1001
1002
$ lexid_incr 1999
22000
$ lexid_incr 1
22
$ lexid_incr 1 -n 100
22
..
28
29
330
331
...
398
399
4400
4401
...In Python.>>> import lexid
>>> lexid.incr("1")
'22'
>>> lexid.incr("0001")
'0002'
>>> lexid.incr("0999")
'11000'To avoid possible zero truncation issues (e.g. with "0001" -> "1") and to reduce rollovers, start at a higher number:>>> lexid.incr("1001")
'1002'
>>> lexid.incr("1002")
'1003'
>>> lexid.incr("1999")
'22000'Lexical IdsThe key thing to look at is how padding may eventually be exhausted.
In order to preserve lexical ordering, build numbers are incremented
in a special way. Examples will perhaps illustrate more clearly."0001""0002""0003"..."0999""11000""11001"..."19998""19999""220000""220001"What is happening here is that the left-most digit is incremented
early/preemptively. Whenever the left-most digit would change, the padding
of the id is expanded through a multiplication by 11.>>>prev_id="0999">>>num_digits=len(prev_id)>>>num_digits4>>>prev_int=int(prev_id,10)>>>prev_int999>>>maybe_next_int=prev_int+1>>>maybe_next_int1000>>>maybe_next_id=f"{maybe_next_int:0{num_digits}}">>>maybe_next_id"1000">>>is_padding_ok=prev_id[0]==maybe_next_id[0]>>>is_padding_okFalse>>>ifis_padding_ok:...# normal case...next_id=maybe_next_id...else:...# extra padding needed...next_int=maybe_next_int*11...next_id=str(next_int)>>>next_id"11000"This behaviour ensures that the following semantic is always preserved:new_version > old_version. This will be true, regardless of padding
expansion. To illustrate the issue this solves, consider what would happen
if we did not expand the padding and instead just incremented numerically."0001""0002""0003"..."0999""1000"..."9999""10000"Here we eventually run into a build number where the lexical ordering is
not preserved, since"10000" > "9999" == False(because the string"1"is lexically smaller than"9"). With large enough padding this may be a
non issue, but it's better to not have to think about it.Just as an example of why lexical ordering is a nice property to have,
there are lots of software which read git tags, but which have no logic to
parse version strings. This software can nonetheless order the version tags
correctly using commonly used lexical ordering. At the most basic
level it can allow you to use the UNIXsortcommand, for example to parse
VCS tags.$printf"v0.9.0\nv0.10.0\nv0.11.0\n"|sort
v0.10.0
v0.11.0
v0.9.0

$printf"v0.9.0\nv0.10.0\nv0.11.0\n"|sort-n
v0.10.0
v0.11.0
v0.9.0

$lexid_incr0997-n5|sort09980999110001100111002This sorting even works correctly in JavaScript!> var versions = ["11002", "11001", "11000", "0999", "0998"];
> versions.sort();
["0998", "0999", "11000", "11001", "11002"]Changelog forhttps://github.com/mbarkhau/lexid2021.1006Minor packaging updates2020.1005Initial release (extracted from pycalver)