gh-117648: Improve performance of os.join by replacing map with a direct method …

[nineteendo]

…call

Benchmark

ntpath.py

script

::test.bat
@echo off
echo 1 item && python -m timeit -s "import before.ntpath" "before.ntpath.join('foo')" && python -m timeit -s "import after.ntpath" "after.ntpath.join('foo')"
echo 10 items && python -m timeit -s "import before.ntpath; paths = ['foo'] * 10" "before.ntpath.join(*paths)" && python -m timeit -s "import after.ntpath; paths = ['foo'] * 10" "after.ntpath.join(*paths)"
echo 100 items && python -m timeit -s "import before.ntpath; paths = ['foo'] * 100" "before.ntpath.join(*paths)" && python -m timeit -s "import after.ntpath; paths = ['foo'] * 100" "after.ntpath.join(*paths)"

1 item
500000 loops, best of 5: 699 nsec per loop # before
500000 loops, best of 5: 612 nsec per loop # after
# -> 1.14x faster
10 items
50000 loops, best of 5: 5.47 usec per loop # before
50000 loops, best of 5: 5.18 usec per loop # after
# -> 1.06x faster
100 items
5000 loops, best of 5: 54.6 usec per loop # before
5000 loops, best of 5: 51.9 usec per loop # after
# -> 1.05x faster

posixpath.py

script

# test.sh
echo 1 item && python -m timeit -s "import before.posixpath" "before.posixpath.join('foo')" && python -m timeit -s "import after.posixpath" "after.posixpath.join('foo')"
echo 10 items && python -m timeit -s "import before.posixpath; paths = ['foo'] * 10" "before.posixpath.join(*paths)" && python -m timeit -s "import after.posixpath; paths = ['foo'] * 10" "after.posixpath.join(*paths)"
echo 100 items && python -m timeit -s "import before.posixpath; paths = ['foo'] * 100" "before.posixpath.join(*paths)" && python -m timeit -s "import after.posixpath; paths = ['foo'] * 100" "after.posixpath.join(*paths)"

1 item
1000000 loops, best of 5: 325 nsec per loop # before
1000000 loops, best of 5: 241 nsec per loop # after
# -> 1.35x faster
10 items
100000 loops, best of 5: 3.33 usec per loop # before
100000 loops, best of 5: 3.32 usec per loop # after
# -> no difference
100 items
10000 loops, best of 5: 33.8 usec per loop # before
10000 loops, best of 5: 34.1 usec per loop # after
# -> no difference

• Issue: Improve performance of os.join by replacing map with a direct method call #117648

[erlend-aasland]

The change itself is minimal, code readability/maintainability is not affected, and the speedup seems good enough to warrant an approval.

I still recommend redirecting your enthusiasm towards triaging the existing issues in the bug-tracker and helping fixing real bugs instead of looking for micro-optimisations. See my comment #117634 (comment).