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.

1 files changed, 8 insertions, 0 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 387c58594e..fa77ec17f5 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):