gh-89727: Improve os.walk complexity and speed

Lib/os.py

@@ -341,11 +341,11 @@ def walk(top, topdown=True, onerror=None, followlinks=False):
  """
  sys.audit("os.walk", top, topdown, onerror, followlinks)
 
- stack = [(False, fspath(top))]
+ stack = [fspath(top)]
  islink, join = path.islink, path.join
  while stack:
-must_yield, top = stack.pop()
- if must_yield:
+ top = stack.pop()
+ if isinstance(top, tuple):
  yield top
  continue
 
@@ -422,13 +422,13 @@ def walk(top, topdown=True, onerror=None, followlinks=False):
  # the caller can replace the directory entry during the "yield"
  # above.
  if followlinks or not islink(new_path):
- stack.append((False, new_path))
+ stack.append(new_path)
  else:
  # Yield after sub-directory traversal if going bottom up
- stack.append((True, (top, dirs, nondirs)))
+ stack.append((top, dirs, nondirs))
  # Traverse into sub-directories
  for new_path in reversed(walk_dirs):
- stack.append((False, new_path))
+ stack.append(new_path)
 
 __all__.append("walk")
 

Misc/NEWS.d/next/Library/2023-01-01-23-57-00.gh-issue-89727.ojedHN.rst

@@ -0,0 +1 @@
+Simplify and optimize :func:`os.walk` by using :func:`isinstance` checks to check the top of the stack.