Fix #11583. Changed os.path.isdir to use GetFileAttributes instead of os.stat.

By changing to the Windows GetFileAttributes API in nt._isdir we can figure
out if the path is a directory without opening the file via os.stat. This has
the minor benefit of speeding up os.path.isdir by at least 2x for regular
files and 10-15x improvements were seen on symbolic links (which opened the
file multiple times during os.stat). Since os.path.isdir is used in
several places on interpreter startup, we get a minor speedup in startup time.

1 files changed, 13 insertions, 0 deletions

diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index ec8a7ab..2483ced 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -672,3 +672,16 @@ except ImportError:
 def sameopenfile(f1, f2):
     """Test whether two file objects reference the same file"""
     return _getfileinformation(f1) == _getfileinformation(f2)
+
+
+try:
+    # The genericpath.isdir implementation uses os.stat and checks the mode
+    # attribute to tell whether or not the path is a directory.
+    # This is overkill on Windows - just pass the path to GetFileAttributes
+    # and check the attribute from there.
+    from nt import _isdir
+except ImportError:
+    from genericpath import isdir as _isdir
+
+def isdir(path):
+    return _isdir(path)