make sure the builtin help function doesn't fail when sys.stdin is not a valid file (closes #11709)

Original patch by Amaury Forgeot d'Arc with a test by bdettmer.

2 files changed, 10 insertions, 0 deletions

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 254fe40..218fd30 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1377,6 +1377,8 @@ def getpager():
     """Decide what method to use for paging through text."""
     if type(sys.stdout) is not types.FileType:
         return plainpager
+    if not hasattr(sys.stdin, "isatty"):
+        return plainpager
     if not sys.stdin.isatty() or not sys.stdout.isatty():
         return plainpager
     if 'PAGER' in os.environ:
diff --git a/Lib/test/test_pydoc.py b/Lib/test/test_pydoc.py
index 7ff8d6d..763c319 100644
--- a/Lib/test/test_pydoc.py
+++ b/Lib/test/test_pydoc.py
@@ -333,6 +333,14 @@ class PydocDocTest(unittest.TestCase):
         result, doc_loc = get_pydoc_text(xml.etree)
         self.assertEqual(doc_loc, "", "MODULE DOCS incorrectly includes a link")
 
+    def test_getpager_with_stdin_none(self):
+        previous_stdin = sys.stdin
+        try:
+            sys.stdin = None
+            pydoc.getpager() # Shouldn't fail.
+        finally:
+            sys.stdin = previous_stdin
+
     def test_non_str_name(self):
         # issue14638
         # Treat illegal (non-str) name like no name