gh-117634: Remove _get_[both]sep[s]() calls in os.path

[nineteendo]

Benchmark

ntpath.py

::test.bat
@echo off
echo split() && python -m timeit -s "import before.ntpath" "before.ntpath.split('foo')" && python -m timeit -s "import after.ntpath" "after.ntpath.split('foo')"
echo ismount() && python -m timeit -s "import before.ntpath" "before.ntpath.ismount('//')" && python -m timeit -s "import after.ntpath" "after.ntpath.ismount('//')"
echo expanduser() && python -m timeit -s "import before.ntpath" "before.ntpath.expanduser('~')" && python -m timeit -s "import after.ntpath" "after.ntpath.expanduser('~')"
echo expanduser('~' + 'a' * 100) && python -m timeit -s "import before.ntpath" "before.ntpath.expanduser('~' + 'a' * 100)" && python -m timeit -s "import after.ntpath" "after.ntpath.expanduser('~' + 'a' * 100)"

split()
500000 loops, best of 5: 867 nsec per loop # before
500000 loops, best of 5: 801 nsec per loop # after
# -> 1.08x faster
ismount()
200000 loops, best of 5: 1.21 usec per loop # before
200000 loops, best of 5: 1.16 usec per loop # after
# -> 1.04x faster
expanduser()
500000 loops, best of 5: 977 nsec per loop # before
500000 loops, best of 5: 965 nsec per loop # after
# -> no difference
expanduser('~' + 'a' * 100)
20000 loops, best of 5: 18 usec per loop # before
20000 loops, best of 5: 11.3 usec per loop # after
# -> 1.59x faster (for long usernames)

posixpath.py

# test.sh
echo "isabs()" && python -m timeit -s "import before.posixpath" "before.posixpath.isabs('/')" && python -m timeit -s "import after.posixpath" "after.posixpath.isabs('/')"
echo "join()" && python -m timeit -s "import before.posixpath" "before.posixpath.join('foo')" && python -m timeit -s "import after.posixpath" "after.posixpath.join('foo')"
echo "split()" && python -m timeit -s "import before.posixpath" "before.posixpath.split('foo')" && python -m timeit -s "import after.posixpath" "after.posixpath.split('foo')"
echo "basename()" && python -m timeit -s "import before.posixpath" "before.posixpath.basename('foo')" && python -m timeit -s "import after.posixpath" "after.posixpath.basename('foo')"
echo "dirname()" && python -m timeit -s "import before.posixpath" "before.posixpath.dirname('foo')" && python -m timeit -s "import after.posixpath" "after.posixpath.dirname('foo')"
echo "expanduser()" && python -m timeit -s "import before.posixpath" "before.posixpath.expanduser('~')" && python -m timeit -s "import after.posixpath" "after.posixpath.expanduser('~')"

isabs()
1000000 loops, best of 5: 235 nsec per loop # before
1000000 loops, best of 5: 204 nsec per loop # after
# -> 1.15x faster
join()
1000000 loops, best of 5: 322 nsec per loop # before
1000000 loops, best of 5: 303 nsec per loop # after
# -> 1.06x faster
split()
1000000 loops, best of 5: 351 nsec per loop # before
1000000 loops, best of 5: 339 nsec per loop # after
# -> 1.04x faster
basename()
1000000 loops, best of 5: 284 nsec per loop # before
1000000 loops, best of 5: 257 nsec per loop # after
# -> 1.11x faster
dirname()
1000000 loops, best of 5: 286 nsec per loop # before
1000000 loops, best of 5: 262 nsec per loop # after
# -> 1.09x faster
expanduser()
200000 loops, best of 5: 1.38 usec per loop # before
200000 loops, best of 5: 1.26 usec per loop # after
# -> 1.10 faster

• Issue: Remove _get_[both]sep[s]() calls in os.path #117634