Issue #15841: The readable(), writable() and seekable() methods of BytesIO

and StringIO objects now raise ValueError when the object has been closed.
Patch by Alessandro Moura.

2 files changed, 11 insertions, 4 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 387c585..fa77ec1 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -895,12 +895,18 @@ class BytesIO(BufferedIOBase):
         return pos
 
     def readable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return True
 
     def writable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return True
 
     def seekable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return True
 
 
@@ -1562,6 +1568,8 @@ class TextIOWrapper(TextIOBase):
         return self._buffer
 
     def seekable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return self._seekable
 
     def readable(self):
diff --git a/Lib/test/test_memoryio.py b/Lib/test/test_memoryio.py
index 04ec8e7..e5db945 100644
--- a/Lib/test/test_memoryio.py
+++ b/Lib/test/test_memoryio.py
@@ -318,9 +318,9 @@ class MemoryTestMixin:
         self.assertEqual(memio.isatty(), False)
         self.assertEqual(memio.closed, False)
         memio.close()
-        self.assertEqual(memio.writable(), True)
-        self.assertEqual(memio.readable(), True)
-        self.assertEqual(memio.seekable(), True)
+        self.assertRaises(ValueError, memio.writable)
+        self.assertRaises(ValueError, memio.readable)
+        self.assertRaises(ValueError, memio.seekable)
         self.assertRaises(ValueError, memio.isatty)
         self.assertEqual(memio.closed, True)
 
@@ -665,7 +665,6 @@ class CBytesIOTest(PyBytesIOTest):
         check(io.BytesIO(b'a'), basesize + 1 + 1 )
         check(io.BytesIO(b'a' * 1000), basesize + 1000 + 1 )
 
-
 class CStringIOTest(PyStringIOTest):
     ioclass = io.StringIO
     UnsupportedOperation = io.UnsupportedOperation