addressed comments on PR

help.txt

@@ -101,6 +101,16 @@ FUNCTIONS
         multipart_upload_kwargs: dict, optional
             Additional parameters to pass to boto3's initiate_multipart_upload function.
             For writing only.
+        singlepart_upload_kwargs: dict, optional
+            Additional parameters to pass to boto3's S3.Object.put function when using single
+            part upload.
+            For writing only.
+        multipart_upload: bool, optional
+            Default: `True`
+            If set to `True`, will use multipart upload for writing to S3. If set
+            to `False`, S3 upload will use the S3 Single-Part Upload API, which
+            is more ideal for small file sizes.
+            For writing only.
         version_id: str, optional
             Version of the object, used when reading object. If None, will fetch the most recent version.
 

smart_open/s3.py

@@ -79,6 +79,7 @@ def open(
         resource_kwargs=None,
         multipart_upload_kwargs=None,
         multipart_upload=True,
+        singlepart_upload_kwargs=None,
         object_kwargs=None,
         ):
     """Open an S3 object for reading or writing.
@@ -102,10 +103,14 @@ def open(
     multipart_upload_kwargs: dict, optional
         Additional parameters to pass to boto3's initiate_multipart_upload function.
         For writing only.
+    singlepart_upload_kwargs: dict, optional
+        Additional parameters to pass to boto3's S3.Object.put function when using single
+        part upload.
+        For writing only.
     multipart_upload: bool, optional
         Default: `True`
         If set to `True`, will use multipart upload for writing to S3. If set
-        to `false`, S3 upload will use the S3 Single-Part Upload API, which
+        to `False`, S3 upload will use the S3 Single-Part Upload API, which
         is more ideal for small file sizes.
         For writing only.
     version_id: str, optional
@@ -155,7 +160,7 @@ def open(
                 bucket_id,
                 key_id,
                 session=session,
-                multipart_upload_kwargs=multipart_upload_kwargs,
+                singlepart_upload_kwargs=singlepart_upload_kwargs,
                 resource_kwargs=resource_kwargs,
             )
     else:
@@ -663,15 +668,18 @@ def __repr__(self):
 class SinglepartWriter(io.BufferedIOBase):
     """Writes bytes to S3 using the single part API.
 
-    Implements the io.BufferedIOBase interface of the standard library."""
+    Implements the io.BufferedIOBase interface of the standard library.
+
+    This class buffers all of its input in memory until its `close` method is called. Only then will
+    the data be written to S3 and the buffer is released."""
 
     def __init__(
             self,
             bucket,
             key,
             session=None,
             resource_kwargs=None,
-            multipart_upload_kwargs=None,
+            singlepart_upload_kwargs=None,
             ):
 
         self._session = session
@@ -681,10 +689,10 @@ def __init__(
             session = boto3.Session()
         if resource_kwargs is None:
             resource_kwargs = {}
-        if multipart_upload_kwargs is None:
-            multipart_upload_kwargs = {}
+        if singlepart_upload_kwargs is None:
+            singlepart_upload_kwargs = {}
 
-        self._multipart_upload_kwargs = multipart_upload_kwargs
+        self._singlepart_upload_kwargs = singlepart_upload_kwargs
 
         s3 = session.resource('s3', **resource_kwargs)
         try:
@@ -712,9 +720,10 @@ def close(self):
         self._buf.seek(0)
 
         try:
-            self._object.put(Body=self._buf, **self._multipart_upload_kwargs)
+            self._object.put(Body=self._buf, **self._singlepart_upload_kwargs)
         except botocore.client.ClientError:
-            raise ValueError('the bucket %r does not exist, or is forbidden for access' % self._object.bucket_name)
+            raise ValueError(
+                'the bucket %r does not exist, or is forbidden for access' % self._object.bucket_name)
 
         logger.debug("direct upload finished")
         self._closed = True
@@ -774,13 +783,13 @@ def __repr__(self):
             "key=%r, "
             "session=%r, "
             "resource_kwargs=%r, "
-            "multipart_upload_kwargs=%r)"
+            "singlepart_upload_kwargs=%r)"
         ) % (
             self._object.bucket_name,
             self._object.key,
             self._session,
             self._resource_kwargs,
-            self._multipart_upload_kwargs,
+            self._singlepart_upload_kwargs,
         )
 
 

smart_open/tests/test_s3.py

@@ -302,7 +302,7 @@ def test_to_boto3(self):
 
 
 @maybe_mock_s3
-class BufferedMultiPartOutputBaseTest(unittest.TestCase):
+class MultipartWriterTest(unittest.TestCase):
     """
     Test writing into s3 files.
 
@@ -318,7 +318,7 @@ def test_write_01(self):
         test_string = u"žluťoučký koníček".encode('utf8')
 
         # write into key
-        with smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fout:
+        with smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fout:
             fout.write(test_string)
 
         # read key and test content
@@ -329,7 +329,7 @@ def test_write_01(self):
     def test_write_01a(self):
         """Does s3 write fail on incorrect input?"""
         try:
-            with smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fin:
+            with smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fin:
                 fin.write(None)
         except TypeError:
             pass
@@ -338,7 +338,7 @@ def test_write_01a(self):
 
     def test_write_02(self):
         """Does s3 write unicode-utf8 conversion work?"""
-        smart_open_write = smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME)
+        smart_open_write = smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME)
         smart_open_write.tell()
         logger.info("smart_open_write: %r", smart_open_write)
         with smart_open_write as fout:
@@ -348,7 +348,7 @@ def test_write_02(self):
     def test_write_03(self):
         """Does s3 multipart chunking work correctly?"""
         # write
-        smart_open_write = smart_open.s3.BufferedMultiPartOutputBase(
+        smart_open_write = smart_open.s3.MultipartWriter(
             BUCKET_NAME, WRITE_KEY_NAME, min_part_size=10
         )
         with smart_open_write as fout:
@@ -369,7 +369,7 @@ def test_write_03(self):
 
     def test_write_04(self):
         """Does writing no data cause key with an empty value to be created?"""
-        smart_open_write = smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME)
+        smart_open_write = smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME)
         with smart_open_write as fout:  # noqa
             pass
 
@@ -380,7 +380,7 @@ def test_write_04(self):
 
     def test_gzip(self):
         expected = u'а не спеть ли мне песню... о любви'.encode('utf-8')
-        with smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fout:
+        with smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fout:
             with gzip.GzipFile(fileobj=fout, mode='w') as zipfile:
                 zipfile.write(expected)
 
@@ -397,7 +397,7 @@ def test_buffered_writer_wrapper_works(self):
         """
         expected = u'не думай о секундах свысока'
 
-        with smart_open.s3.BufferedMultiPartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fout:
+        with smart_open.s3.MultipartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fout:
             with io.BufferedWriter(fout) as sub_out:
                 sub_out.write(expected.encode('utf-8'))
 
@@ -451,7 +451,7 @@ def test_to_boto3(self):
 
 
 @maybe_mock_s3
-class BufferedSinglePartOutputBaseTest(unittest.TestCase):
+class SinglepartWriterTest(unittest.TestCase):
     """
     Test writing into s3 files using single part upload.
 
@@ -467,7 +467,7 @@ def test_write_01(self):
         test_string = u"žluťoučký koníček".encode('utf8')
 
         # write into key
-        with smart_open.s3.BufferedSinglePartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fout:
+        with smart_open.s3.SinglepartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fout:
             fout.write(test_string)
 
         # read key and test content
@@ -478,7 +478,7 @@ def test_write_01(self):
     def test_write_01a(self):
         """Does s3 write fail on incorrect input?"""
         try:
-            with smart_open.s3.BufferedSinglePartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fin:
+            with smart_open.s3.SinglepartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fin:
                 fin.write(None)
         except TypeError:
             pass
@@ -489,7 +489,7 @@ def test_write_02(self):
         """Does s3 write unicode-utf8 conversion work?"""
         test_string = u"testžížáč".encode("utf-8")
 
-        smart_open_write = smart_open.s3.BufferedSinglePartOutputBase(BUCKET_NAME, WRITE_KEY_NAME)
+        smart_open_write = smart_open.s3.SinglepartWriter(BUCKET_NAME, WRITE_KEY_NAME)
         smart_open_write.tell()
         logger.info("smart_open_write: %r", smart_open_write)
         with smart_open_write as fout:
@@ -498,7 +498,7 @@ def test_write_02(self):
 
     def test_write_04(self):
         """Does writing no data cause key with an empty value to be created?"""
-        smart_open_write = smart_open.s3.BufferedSinglePartOutputBase(BUCKET_NAME, WRITE_KEY_NAME)
+        smart_open_write = smart_open.s3.SinglepartWriter(BUCKET_NAME, WRITE_KEY_NAME)
         with smart_open_write as fout:  # noqa
             pass
 
@@ -514,7 +514,7 @@ def test_buffered_writer_wrapper_works(self):
         """
         expected = u'не думай о секундах свысока'
 
-        with smart_open.s3.BufferedSinglePartOutputBase(BUCKET_NAME, WRITE_KEY_NAME) as fout:
+        with smart_open.s3.SinglepartWriter(BUCKET_NAME, WRITE_KEY_NAME) as fout:
             with io.BufferedWriter(fout) as sub_out:
                 sub_out.write(expected.encode('utf-8'))