Make the pdb displayhook compatible with the standard displayhook: do not print Nones. Add a test for that.

1 files changed, 3 insertions, 1 deletions

diff --git a/Lib/pdb.py b/Lib/pdb.py
index eae6296..0751c17 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -210,7 +210,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         """Custom displayhook for the exec in default(), which prevents
         assignment of the _ variable in the builtins.
         """
-        print repr(obj)
+        # reproduce the behavior of the standard displayhook, not printing None
+        if obj is not None:
+            print repr(obj)
 
     def default(self, line):
         if line[:1] == '!': line = line[1:]