[From http://stackoverflow.com/questions/12648737/huge-memory-leak-in-repeated-os-path-isdir-calls]

os.path.isdir() leaks memory under Windows in Python 2.7. The core cause is this snippet:

Modules/posixmodule.c:4226:
    if (!PyArg_ParseTuple(args, "et:_isdir",
                          Py_FileSystemDefaultEncoding, &path))
        return NULL;

    attributes = GetFileAttributesA(path);
    if (attributes == INVALID_FILE_ATTRIBUTES)
        Py_RETURN_FALSE;

check:
    if (attributes & FILE_ATTRIBUTE_DIRECTORY)
        Py_RETURN_TRUE;
    else
        Py_RETURN_FALSE;


The buffer returned by the "et" ParseTuple format must be freed after use. Since it isn't freed, we get a memory leak here.

Patch:

--- a/Modules/posixmodule.c	Mon Apr 09 19:04:04 2012 -0400
+++ b/Modules/posixmodule.c	Sun Jan 27 04:10:34 2013 -0500
@@ -4226,6 +4226,7 @@
         return NULL;
 
     attributes = GetFileAttributesA(path);
+    PyMem_Free(path);
     if (attributes == INVALID_FILE_ATTRIBUTES)
         Py_RETURN_FALSE;