closes bpo-27805: Ignore ESPIPE in initializing seek of append-mode files. (GH-17112)
This change, which follows the behavior of C stdio's fdopen and Python 2's file object, allows pipes to be opened in append mode.
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index e819b0a..4c24146 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1577,7 +1577,11 @@
# For consistent behaviour, we explicitly seek to the
# end of file (otherwise, it might be done only on the
# first write()).
- os.lseek(fd, 0, SEEK_END)
+ try:
+ os.lseek(fd, 0, SEEK_END)
+ except OSError as e:
+ if e.errno != errno.ESPIPE:
+ raise
except:
if owned_fd is not None:
os.close(owned_fd)
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index ad22dfe..501e931 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -3906,6 +3906,17 @@
self.open(support.TESTFN, mode)
self.assertIn('invalid mode', str(cm.exception))
+ def test_open_pipe_with_append(self):
+ # bpo-27805: Ignore ESPIPE from lseek() in open().
+ r, w = os.pipe()
+ self.addCleanup(os.close, r)
+ f = self.open(w, 'a')
+ self.addCleanup(f.close)
+ # Check that the file is marked non-seekable. On Windows, however, lseek
+ # somehow succeeds on pipes.
+ if sys.platform != 'win32':
+ self.assertFalse(f.seekable())
+
def test_io_after_close(self):
for kwargs in [
{"mode": "w"},