Issue #18878: sunau.open now supports the context manager protocol. Based on

patches by Claudiu Popa and R. David Murray.

Doc/whatsnew/3.4.rst

@@ -374,6 +374,8 @@ sunau
 The :meth:`~sunau.getparams` method now returns a namedtuple rather than a
 plain tuple.  (Contributed by Claudiu Popa in :issue:`18901`.)
 
+:meth:`sunau.open` now supports the context manager protocol (:issue:`18878`).
+
 
 urllib
 ------

Lib/sunau.py

@@ -168,6 +168,12 @@ class Au_read:
         if self._file:
             self.close()
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
     def initfp(self, file):
         self._file = file
         self._soundpos = 0
@@ -303,6 +309,12 @@ class Au_write:
             self.close()
         self._file = None
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
     def initfp(self, file):
         self._file = file
         self._framerate = 0
@@ -410,14 +422,17 @@ class Au_write:
             self._patchheader()
 
     def close(self):
-        self._ensure_header_written()
-        if self._nframeswritten != self._nframes or \
-                  self._datalength != self._datawritten:
-            self._patchheader()
-        self._file.flush()
-        if self._opened and self._file:
-            self._file.close()
-        self._file = None
+        if self._file:
+            try:
+                self._ensure_header_written()
+                if self._nframeswritten != self._nframes or \
+                        self._datalength != self._datawritten:
+                    self._patchheader()
+                self._file.flush()
+            finally:
+                if self._opened and self._file:
+                    self._file.close()
+                self._file = None
 
     #
     # private methods

Lib/test/test_sunau.py

-from test.support import run_unittest, TESTFN
+from test.support import TESTFN, unlink
 import unittest
 import pickle
 import os
@@ -18,10 +18,7 @@ class SunAUTest(unittest.TestCase):
     def tearDown(self):
         if self.f is not None:
             self.f.close()
-        try:
-            os.remove(TESTFN)
-        except OSError:
-            pass
+        unlink(TESTFN)
 
     def test_lin(self):
         self.f = sunau.open(TESTFN, 'w')
@@ -84,9 +81,49 @@ class SunAUTest(unittest.TestCase):
         dump = pickle.dumps(params)
         self.assertEqual(pickle.loads(dump), params)
 
+    def test_write_context_manager_calls_close(self):
+        # Close checks for a minimum header and will raise an error
+        # if it is not set, so this proves that close is called.
+        with self.assertRaises(sunau.Error):
+            with sunau.open(TESTFN, 'wb') as f:
+                pass
+        with self.assertRaises(sunau.Error):
+            with open(TESTFN, 'wb') as testfile:
+                with sunau.open(testfile):
+                    pass
+
+    def test_context_manager_with_open_file(self):
+        with open(TESTFN, 'wb') as testfile:
+            with sunau.open(testfile) as f:
+                f.setnchannels(nchannels)
+                f.setsampwidth(sampwidth)
+                f.setframerate(framerate)
+            self.assertFalse(testfile.closed)
+        with open(TESTFN, 'rb') as testfile:
+            with sunau.open(testfile) as f:
+                self.assertFalse(f.getfp().closed)
+                params = f.getparams()
+                self.assertEqual(params[0], nchannels)
+                self.assertEqual(params[1], sampwidth)
+                self.assertEqual(params[2], framerate)
+            self.assertIsNone(f.getfp())
+            self.assertFalse(testfile.closed)
+
+    def test_context_manager_with_filename(self):
+        # If the file doesn't get closed, this test won't fail, but it will
+        # produce a resource leak warning.
+        with sunau.open(TESTFN, 'wb') as f:
+            f.setnchannels(nchannels)
+            f.setsampwidth(sampwidth)
+            f.setframerate(framerate)
+        with sunau.open(TESTFN) as f:
+            self.assertFalse(f.getfp().closed)
+            params = f.getparams()
+            self.assertEqual(params[0], nchannels)
+            self.assertEqual(params[1], sampwidth)
+            self.assertEqual(params[2], framerate)
+        self.assertIsNone(f.getfp())
 
-def test_main():
-    run_unittest(SunAUTest)
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS

@@ -54,6 +54,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #18878: sunau.open now supports the context manager protocol.  Based on
+  patches by Claudiu Popa and R. David Murray.
+
 - Issue #18909: Fix _tkinter.tkapp.interpaddr() on Windows 64-bit, don't cast
   64-bit pointer to long (32 bits).