clarify when the list of subdirectories is read (closes #13779)

1 files changed, 5 insertions, 3 deletions

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 20f3b25..ce19fd26 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -2228,9 +2228,11 @@ features:
 
    If optional argument *topdown* is ``True`` or not specified, the triple for a
    directory is generated before the triples for any of its subdirectories
-   (directories are generated top-down).  If *topdown* is ``False``, the triple for a
-   directory is generated after the triples for all of its subdirectories
-   (directories are generated bottom-up).
+   (directories are generated top-down).  If *topdown* is ``False``, the triple
+   for a directory is generated after the triples for all of its subdirectories
+   (directories are generated bottom-up). No matter the value of *topdown*, the
+   list of subdirectories is retrieved before the tuples for the directory and
+   its subdirectories are generated.
 
    When *topdown* is ``True``, the caller can modify the *dirnames* list in-place
    (perhaps using :keyword:`del` or slice assignment), and :func:`walk` will only