#4408: document regex.groups.
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index c9466af..916feca 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -750,6 +750,11 @@
    were provided.
 
 
+.. attribute:: RegexObject.groups
+
+   The number of capturing groups in the pattern.
+
+
 .. attribute:: RegexObject.groupindex
 
    A dictionary mapping any symbolic group names defined by ``(?P<id>)`` to group