Compare subdirectory generator using os.walk() with one using scandir.scandir()

walk_subdirs.py

"""Compare two ways to iterate over subdirectories of a tree."""

from collections.abc import Iterator
import os
import platform
import time

START_DIR = 'c:\\Users' if platform.system() == 'Windows' else '/usr'


def itersubdirs_walk(start_dir: os.PathLike | str) -> Iterator[str]:
    for root, dirs, _ in os.walk(start_dir):
        for d in dirs:
            yield os.path.join(root, d)


def itersubdirs_scandir(start_dir: os.PathLike | str) ->  Iterator[str]:
    stack = [start_dir]
    while stack:
        root = stack.pop()

        try:
            dentries = os.scandir(root)
        except OSError:
            continue

        dirs = []
        for d in dentries:
            if d.is_dir():
                yield d.path
                dirs.append(d.path)

        stack.extend(reversed(dirs))


results = []

for func in (itersubdirs_walk, itersubdirs_scandir):
    print(func)

    start = time.perf_counter_ns()

    result = list(func(START_DIR))
    results.append(result)

    print((time.perf_counter_ns() - start) / 1_000_000_000)

    print(*result[:20], sep='\n')
    print(len(result))

assert results[0] == results[1]