More glider hacks: implement public keys.

git-svn-id: file:///home/or/svnrepo/updater/trunk@16917 55e972cd-5a19-0410-ae62-a4d7a52db4cd

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/sexp/access.py b/lib/sexp/access.py
index beb87c9..c5182f0 100644
--- a/lib/sexp/access.py
+++ b/lib/sexp/access.py
@@ -36,6 +36,16 @@ def s_child(s, tag):
             return child
     return None
 
+def s_attr(s, tag):
+    """Returns the second element of the child of 's' whose tag is 'tag'.
+       This is helpful for extracting a (key val) element.  Returns None
+       if there is no such element.
+    """
+    ch = s_child(s,tag)
+    if ch == None or len(ch) < 2:
+        return None
+    return ch[1]
+
 def s_children(s, tag):
     """Returns a generator yielding all children of 's' whose tag is 'tag'.