@@ -104,7 +104,7 @@ class Config(object):

     enable = None

     get_continue = False

     put_continue = False

-    upload_id = None

+    upload_id = u""

     skip_existing = False

     recursive = False

     restore_days = 1

@@ -189,8 +189,8 @@ class Config(object):

     limitrate = 0

     requester_pays = False

     stop_on_error = False

-    content_disposition = None

-    content_type = None

+    content_disposition = u""

+    content_type = u""

     stats = False

     # Disabled by default because can create a latency with a CONTINUE status reply

     # expected for every send file requests.

@@ -149,19 +149,19 @@ def sign_url_base_v2(**parms):

     debug("Expiry interpreted as epoch time %s", parms['expiry'])

     signtext = 'GET\n\n\n%(expiry)d\n/%(bucket)s/%(object)s' % parms

     param_separator = '?'

-    if content_disposition is not None:

+    if content_disposition:

         signtext += param_separator + 'response-content-disposition=' + content_disposition

         param_separator = '&'

-    if content_type is not None:

+    if content_type:

         signtext += param_separator + 'response-content-type=' + content_type

         param_separator = '&'

     debug("Signing plaintext: %r", signtext)

     parms['sig'] = s3_quote(sign_string_v2(encode_to_s3(signtext)), unicode_output=True)

     debug("Urlencoded signature: %s", parms['sig'])

     url = "%(proto)s://%(bucket)s.%(host_base)s/%(object)s?AWSAccessKeyId=%(access_key)s&Expires=%(expiry)d&Signature=%(sig)s" % parms

-    if content_disposition is not None:

+    if content_disposition:

         url += "&response-content-disposition=" + s3_quote(content_disposition, unicode_output=True)

-    if content_type is not None:

+    if content_type:

         url += "&response-content-type=" + s3_quote(content_type, unicode_output=True)

     return url

@@ -40,7 +40,7 @@ class MultiPartUpload(object):

         return parts

     def get_unique_upload_id(self, uri):

-        upload_id = None

+        upload_id = ""

         multipart_response = self.s3.get_multipart(uri)

         tree = getTreeFromXml(multipart_response['data'])

         for mpupload in parseNodes(tree):

@@ -49,7 +49,7 @@ class MultiPartUpload(object):

                 mp_path = mpupload['Key']

                 info("mp_path: %s, object: %s" % (mp_path, uri.object()))

                 if mp_path == uri.object():

-                    if upload_id is not None:

+                    if upload_id:

                         raise ValueError("More than one UploadId for URI %s.  Disable multipart upload, or use\n %s multipart %s\nto list the Ids, then pass a unique --upload-id into the put command." % (uri, sys.argv[0], uri))

                     upload_id = mp_upload_id

             except KeyError:

@@ -62,14 +62,14 @@ class MultiPartUpload(object):

         Begin a multipart upload

         http://docs.amazonwebservices.com/AmazonS3/latest/API/index.html?mpUploadInitiate.html

         """

-        if self.s3.config.upload_id is not None:

+        if self.s3.config.upload_id:

             self.upload_id = self.s3.config.upload_id

         elif self.s3.config.put_continue:

             self.upload_id = self.get_unique_upload_id(self.uri)

         else:

-            self.upload_id = None

+            self.upload_id = ""

-        if self.upload_id is None:

+        if not self.upload_id:

             request = self.s3.create_request("OBJECT_POST", uri = self.uri,

                                              headers = self.headers_baseline,

                                              uri_params = {'uploads': None})

@@ -582,7 +582,7 @@ class S3(object):

     def stdin_content_type(self):

         content_type = self.config.mime_type

-        if content_type == '':

+        if not content_type:

             content_type = self.config.default_mime_type

         content_type += "; charset=" + self.config.encoding.upper()

@@ -2875,7 +2875,7 @@ def main():

         raise ParameterError("Chunk size %d MB is too large, must be <= %d MB. Please adjust --multipart-chunk-size-mb" % (cfg.multipart_chunk_size_mb, MultiPartUpload.MAX_CHUNK_SIZE_MB))

     ## If an UploadId was provided, set put_continue True

-    if options.upload_id is not None:

+    if options.upload_id:

         cfg.upload_id = options.upload_id

         cfg.put_continue = True