Improve parse_bytes util method

Signed-off-by: Joffrey F <joffrey@docker.com>

docker/utils/utils.py

@@ -518,9 +518,11 @@ def longint(n):
 
 
 def parse_bytes(s):
+    if isinstance(s, six.integer_types + (float,)):
+        return s
     if len(s) == 0:
-        s = 0
-    else:
+        return 0
+
     if s[-2:-1].isalpha() and s[-1].isalpha():
         if s[-1] == "b" or s[-1] == "B":
             s = s[:-1]
@@ -594,16 +596,10 @@ def create_host_config(binds=None, port_bindings=None, lxc_conf=None,
         version = constants.DEFAULT_DOCKER_API_VERSION
 
     if mem_limit is not None:
-        if isinstance(mem_limit, six.string_types):
-            mem_limit = parse_bytes(mem_limit)
-
-        host_config['Memory'] = mem_limit
+        host_config['Memory'] = parse_bytes(mem_limit)
 
     if memswap_limit is not None:
-        if isinstance(memswap_limit, six.string_types):
-            memswap_limit = parse_bytes(memswap_limit)
-
-        host_config['MemorySwap'] = memswap_limit
+        host_config['MemorySwap'] = parse_bytes(memswap_limit)
 
     if mem_swappiness is not None:
         if version_lt(version, '1.20'):
@@ -873,9 +869,9 @@ def create_container_config(
     if isinstance(labels, list):
         labels = dict((lbl, six.text_type('')) for lbl in labels)
 
-    if isinstance(mem_limit, six.string_types):
+    if mem_limit is not None:
         mem_limit = parse_bytes(mem_limit)
-    if isinstance(memswap_limit, six.string_types):
+    if memswap_limit is not None:
         memswap_limit = parse_bytes(memswap_limit)
 
     if isinstance(ports, list):

tests/integration/container_test.py

@@ -1045,7 +1045,7 @@ class ContainerUpdateTest(helpers.BaseTestCase):
         )
         self.tmp_containers.append(container)
         self.client.start(container)
-        print(self.client.update_container(container, mem_limit=new_mem_limit))
+        self.client.update_container(container, mem_limit=new_mem_limit)
         inspect_data = self.client.inspect_container(container)
         self.assertEqual(inspect_data['HostConfig']['Memory'], new_mem_limit)
         self.assertEqual(inspect_data['HostConfig']['CpuShares'], 102)