diff -r 7757e98a9f3b Lib/gzip.py
--- a/Lib/gzip.py	Tue Mar 17 06:56:11 2015 +0200
+++ b/Lib/gzip.py	Fri Mar 20 14:13:11 2015 +0100
@@ -334,17 +334,20 @@
         if self.fileobj is None:
             raise ValueError("write() on closed GzipFile object")
 
-        # Convert data type if called by io.BufferedWriter.
-        if isinstance(data, memoryview):
-            data = data.tobytes()
+        if isinstance(data, bytes):
+            length = len(data)
+        else:
+            # accept any data that supports the buffer protocol
+            data = memoryview(data)
+            length = data.nbytes
 
-        if len(data) > 0:
-            self.size = self.size + len(data)
+        if length > 0:
+            self.fileobj.write( self.compress.compress(data) )
+            self.size = self.size + length
             self.crc = zlib.crc32(data, self.crc) & 0xffffffff
-            self.fileobj.write( self.compress.compress(data) )
-            self.offset += len(data)
+            self.offset += length
 
-        return len(data)
+        return length
 
     def read(self, size=-1):
         self._check_closed()
diff -r 7757e98a9f3b Lib/test/test_gzip.py
--- a/Lib/test/test_gzip.py	Tue Mar 17 06:56:11 2015 +0200
+++ b/Lib/test/test_gzip.py	Fri Mar 20 14:13:11 2015 +0100
@@ -130,6 +130,40 @@
                 if not ztxt: break
         self.assertEqual(contents, b'a'*201)
 
+    def test_write_memoryview(self):
+        # Test that write accepts a memoryview instead of bytes
+        # and that the data written equals memoryview.tobytes().
+        m = memoryview(data1 * 50)
+        with gzip.GzipFile(self.filename, 'wb') as f:
+            f.write(m)
+        with gzip.GzipFile(self.filename, 'rb') as f:
+            self.assertEqual(f.read(), data1 * 50)
+        m = memoryview(bytes(range(256)))
+        n = m.cast('B', shape=[8,8,4])
+        with gzip.GzipFile(self.filename, 'wb') as f:
+            f.write(n)
+        with gzip.GzipFile(self.filename, 'rb') as f:
+            self.assertEqual(f.read(), m.tobytes())
+    
+    def test_write_misc_data(self):
+        # Test that any binary sequence type can be written
+        # and that other types raise TypeError.
+        with gzip.GzipFile(self.filename, 'wb') as f:
+            bytes_like_types = { bytes, bytearray }
+            data = (bytearray(data1), data1.decode('utf-8'),
+                    list(data1), data1)
+            for d in data:
+                try:
+                    f.write(d)
+                except TypeError:
+                    self.assertNotIn(type(d), bytes_like_types)
+                else:
+                    self.assertIn(type(d), bytes_like_types)
+        with gzip.GzipFile(self.filename, 'rb') as f:
+            self.assertEqual(f.read(),
+                b''.join(bytes(d) for d in data 
+                if type(d) in bytes_like_types))
+                      
     def test_exclusive_write(self):
         with gzip.GzipFile(self.filename, 'xb') as f:
             f.write(data1 * 50)