diff -r e548ab4ce71d Doc/library/http.client.rst
--- a/Doc/library/http.client.rst	Mon Feb 09 19:49:00 2015 +0000
+++ b/Doc/library/http.client.rst	Thu Feb 12 21:38:47 2015 -0800
@@ -212,8 +212,10 @@
    contents of the file is sent; this file object should support ``fileno()``
    and ``read()`` methods. The header Content-Length is automatically set to
    the length of the file as reported by stat. The *body* argument may also be
-   an iterable and Content-Length header should be explicitly provided when the
-   body is an iterable.
+   an iterable. If the iterable is a tuple or list and all elements are bytes
+   objects, the Content-Length will automatically be set if not already
+   supplied in the request headers. In all other iterable cases, the
+   Content-Length header should be explicitly provided.
 
    The *headers* argument should be a mapping of extra HTTP
    headers to send with the request.
@@ -221,6 +223,11 @@
    .. versionadded:: 3.2
       *body* can now be an iterable.
 
+   .. versionadded:: 3.5
+      The Content-Length header will be set when *body* is a list or tuple
+      comprised only of bytes objects. 
+
+
 .. method:: HTTPConnection.getresponse()
 
    Should be called after a request is sent to get the response from the server.
diff -r e548ab4ce71d Lib/http/client.py
--- a/Lib/http/client.py	Mon Feb 09 19:49:00 2015 +0000
+++ b/Lib/http/client.py	Thu Feb 12 21:38:47 2015 -0800
@@ -841,6 +841,8 @@
         except TypeError:
             if isinstance(data, collections.Iterable):
                 for d in data:
+                    if hasattr(d, 'encode'):
+                        d = d.encode('iso-8859-1')
                     self.sock.sendall(d)
             else:
                 raise TypeError("data should be a bytes-like object "
@@ -1031,20 +1033,29 @@
 
     def _set_content_length(self, body):
         # Set the content-length based on the body.
-        thelen = None
-        try:
-            thelen = str(len(body))
-        except TypeError as te:
-            # If this is a file-like object, try to
-            # fstat its file descriptor
+        size = None
+        if isinstance(body, (list, tuple)):
+            # there are a couple of ways to do this: only calculate the
+            # content-length if all elements in a list or tuple are bytes, or
+            # worst case, keep a copy of the entire encoded body in memory and
+            # pass it along to send(). as the former is the least intrusive
+            # in terms of memory (iterables are encoded on the fly in
+            # send()), that's the path taken here.
+            if all(isinstance(line, bytes) for line in body):
+                size = sum(len(line) for line in body)
+        else:
             try:
-                thelen = str(os.fstat(body.fileno()).st_size)
-            except (AttributeError, OSError):
-                # Don't send a length if this failed
-                if self.debuglevel > 0: print("Cannot stat!!")
+                size = len(body)
+            except TypeError:
+                try:
+                    size = os.fstat(body.fileno()).st_size
+                except (AttributeError, OSError):
+                    if self.debuglevel > 0:
+                        print("Cannot stat!!")
+                    size = None
 
-        if thelen is not None:
-            self.putheader('Content-Length', thelen)
+        if size is not None:
+            self.putheader('Content-Length', size)
 
     def _send_request(self, method, url, body, headers):
         # Honor explicitly requested Host: and Accept-Encoding: headers.
diff -r e548ab4ce71d Lib/test/test_httplib.py
--- a/Lib/test/test_httplib.py	Mon Feb 09 19:49:00 2015 +0000
+++ b/Lib/test/test_httplib.py	Thu Feb 12 21:38:47 2015 -0800
@@ -1161,7 +1161,6 @@
     def setUp(self):
         self.conn = client.HTTPConnection('example.com')
         self.conn.sock = self.sock = FakeSocket("")
-        self.conn.sock = self.sock
 
     def get_headers_and_fp(self):
         f = io.BytesIO(self.sock.data)
@@ -1226,6 +1225,25 @@
             self.assertEqual("5", message.get("content-length"))
             self.assertEqual(b'body\xc1', f.read())
 
+    def test_list_body(self):
+        cases = (
+            ([b'foo', b'bar'], b'foobar', '6'),
+            ((b'foo', b'bar'), b'foobar', '6'),
+            ((b'foo', 'bar'), b'foobar', None),
+            ([b'foo', 'bar'], b'foobar', None),
+        )
+        with self.subTest():
+            for body, expected, expected_len in cases:
+                self.conn = client.HTTPConnection('example.com')
+                self.conn.sock = self.sock = FakeSocket('')
+
+                self.conn.request('PUT', '/url', body)
+                msg, f = self.get_headers_and_fp()
+                self.assertEqual('text/plain', msg.get_content_type())
+                self.assertIsNone(msg.get_charset())
+                self.assertEqual(expected_len, msg.get('content-length'))
+                self.assertEqual(expected, f.read())
+
 
 class HTTPResponseTest(TestCase):