[Python] Enable and apply pylint

Ref husky-team#3.

.travis.yml

@@ -2,7 +2,7 @@ sudo: required
 
 dist: trusty
 
-language: python  # workaround for not setting CC/CXX with default value
+language: python
 
 addons:
   apt:
@@ -26,6 +26,7 @@ before_install:
   - sudo apt-get -y install libboost-{chrono,program-options,date-time,thread,system,filesystem,regex,serialization}1.58{-dev,.0}
 
 install:
+  # For c++ dependencies
   - mkdir tmp
   - cd tmp
   - git clone https://github.com/zeromq/cppzmq
@@ -35,11 +36,18 @@ install:
   - cd ../..
   - rm -rf tmp
 
+  # For python dependencies
+  - pip install pylint
+  - pip install zmq
+  - pip install cloudpickle
+  - pip install msgpack
+
 before_script:
   - export PYHUSKY_ROOT=.
   - export CLANG_FORMAT=clang-format-3.8
   - ./scripts/lint.py
   - ./scripts/clang-format.py -o check
+  - ./scripts/pylint.py
 
 matrix:
   include:

python/pyhusky/backend/globalvar.py

@@ -12,16 +12,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import sys
 import zmq
 
-class OperationParam:
+class OperationParam(object):
     data_str = "data"
     url_str = "url"
     lambda_str = "lambda"
     list_str = "list_name"
 
-class GlobalVar:
+    def __init__(self):
+        pass
+
+class GlobalVar(object):
     actiontype = "action"
     transformationtype = "transformation"
     loadtype = "load"
@@ -32,7 +34,13 @@ class GlobalVar:
     name_to_prefunc = dict()
     name_to_postfunc = dict()
 
-class GlobalSocket:
+    def __init__(self):
+        pass
+
+class GlobalSocket(object):
+    def __init__(self):
+        pass
+
     # pipe_from_cpp
     # pipe_to_cpp
     @staticmethod
@@ -51,18 +59,15 @@ def send(content):
     def recv():
         return GlobalSocket.pipe_from_cpp.recv()
 
-# N2N
-import threading
-
-class GlobalN2NSocket:
+class GlobalN2NSocket(object):
     @staticmethod
     def init_socket():
         ctx = zmq.Context()
         comm_port = int(GlobalSocket.recv()) + 1
         GlobalN2NSocket.puller = ctx.socket(zmq.PULL)
         GlobalN2NSocket.puller.bind("tcp://0.0.0.0:" + str(comm_port + GlobalVar.local_id))
         GlobalN2NSocket.pushers = []
-        for i in xrange(int(GlobalSocket.recv())):
+        for _ in xrange(int(GlobalSocket.recv())):
             host = "tcp://" + GlobalSocket.recv() + ":"
             for j in xrange(int(GlobalSocket.recv())):
                 sock = ctx.socket(zmq.PUSH)
@@ -76,5 +81,3 @@ def send(dst, msg):
     @staticmethod
     def recv():
         return GlobalN2NSocket.puller.recv()
-
-# N2N