diff --git a/account/decorators.py b/account/decorators.py
index baa7aad5..f801f95f 100644
--- a/account/decorators.py
+++ b/account/decorators.py
@@ -1,9 +1,9 @@
-from __future__ import unicode_literals
 import functools
 
 from django.utils.translation import ugettext as _
 
 from utils.api import JSONResponse
+
 from .models import AdminType
 
 
diff --git a/account/middleware.py b/account/middleware.py
index e494f1a0..29e1ea77 100644
--- a/account/middleware.py
+++ b/account/middleware.py
@@ -1,8 +1,10 @@
 import time
-from django.utils.translation import ugettext as _
+
 from django.contrib import auth
+from django.utils.translation import ugettext as _
 
 from utils.api import JSONResponse
+
 from .models import AdminType
 
 
diff --git a/account/migrations/0001_initial.py b/account/migrations/0001_initial.py
index a028551e..c6de9c38 100644
--- a/account/migrations/0001_initial.py
+++ b/account/migrations/0001_initial.py
@@ -2,11 +2,12 @@
 # Generated by Django 1.9.12 on 2017-01-23 07:59
 from __future__ import unicode_literals
 
-import account.models
-from django.conf import settings
-from django.db import migrations, models
 import django.db.models.deletion
 import jsonfield.fields
+from django.conf import settings
+from django.db import migrations, models
+
+import account.models
 
 
 class Migration(migrations.Migration):
diff --git a/account/serializers.py b/account/serializers.py
index 77c9cdc1..04d2a8e3 100644
--- a/account/serializers.py
+++ b/account/serializers.py
@@ -1,6 +1,6 @@
-from utils.api import serializers, DateTimeTZField
+from utils.api import DateTimeTZField, serializers
 
-from .models import User, AdminType
+from .models import AdminType, User
 
 
 class UserLoginSerializer(serializers.Serializer):
diff --git a/account/tests.py b/account/tests.py
index f8fcd171..04ed9c78 100644
--- a/account/tests.py
+++ b/account/tests.py
@@ -3,12 +3,12 @@ from unittest import mock
 
 from django.contrib import auth
 from django.utils.translation import ugettext as _
-
 from otpauth import OtpAuth
-from utils.shortcuts import rand_str
-from utils.api.tests import APITestCase, APIClient
 
-from .models import User, AdminType
+from utils.api.tests import APIClient, APITestCase
+from utils.shortcuts import rand_str
+
+from .models import AdminType, User
 
 
 class PermissionDecoratorTest(APITestCase):
diff --git a/account/urls/oj.py b/account/urls/oj.py
index bdcde3c5..6a1ef6c1 100644
--- a/account/urls/oj.py
+++ b/account/urls/oj.py
@@ -1,6 +1,6 @@
 from django.conf.urls import url
 
-from ..views.oj import UserLoginAPI, UserRegisterAPI, UserChangePasswordAPI
+from ..views.oj import UserChangePasswordAPI, UserLoginAPI, UserRegisterAPI
 
 urlpatterns = [
     url(r"^login$", UserLoginAPI.as_view(), name="user_login_api"),
diff --git a/account/views/admin.py b/account/views/admin.py
index a5d94891..e818b0a2 100644
--- a/account/views/admin.py
+++ b/account/views/admin.py
@@ -1,5 +1,3 @@
-from __future__ import unicode_literals
-
 from django.core.exceptions import MultipleObjectsReturned
 from django.db.models import Q
 from django.utils.translation import ugettext as _
@@ -9,7 +7,7 @@ from utils.shortcuts import rand_str
 
 from ..decorators import super_admin_required
 from ..models import User
-from ..serializers import (UserSerializer, EditUserSerializer)
+from ..serializers import EditUserSerializer, UserSerializer
 
 
 class UserAdminAPI(APIView):
diff --git a/account/views/oj.py b/account/views/oj.py
index fb501990..3e48a120 100644
--- a/account/views/oj.py
+++ b/account/views/oj.py
@@ -1,15 +1,15 @@
 from django.contrib import auth
 from django.core.exceptions import MultipleObjectsReturned
 from django.utils.translation import ugettext as _
-
 from otpauth import OtpAuth
 
 from utils.api import APIView, validate_serializer
 from utils.captcha import Captcha
+
 from ..decorators import login_required
 from ..models import User, UserProfile
-from ..serializers import (UserLoginSerializer, UserRegisterSerializer,
-                           UserChangePasswordSerializer)
+from ..serializers import (UserChangePasswordSerializer, UserLoginSerializer,
+                           UserRegisterSerializer)
 
 
 class UserLoginAPI(APIView):
diff --git a/announcement/migrations/0001_initial.py b/announcement/migrations/0001_initial.py
index 345a10f6..cd92e223 100644
--- a/announcement/migrations/0001_initial.py
+++ b/announcement/migrations/0001_initial.py
@@ -2,9 +2,10 @@
 # Generated by Django 1.9.12 on 2017-01-23 07:59
 from __future__ import unicode_literals
 
+import django.db.models.deletion
 from django.conf import settings
 from django.db import migrations, models
-import django.db.models.deletion
+
 import utils.models
 
 
diff --git a/announcement/serializers.py b/announcement/serializers.py
index 72393c8f..f1a5f494 100644
--- a/announcement/serializers.py
+++ b/announcement/serializers.py
@@ -1,7 +1,7 @@
-from utils.api import serializers
-
 from account.models import User
+from utils.api import serializers
 from utils.api._serializers import DateTimeTZField
+
 from .models import Announcement
 
 
diff --git a/announcement/views.py b/announcement/views.py
index dbb3c6bb..04abf2cf 100644
--- a/announcement/views.py
+++ b/announcement/views.py
@@ -1,10 +1,10 @@
 from django.utils.translation import ugettext as _
 
 from account.decorators import super_admin_required
-from utils.api import APIView, validate_serializer, IDOnlySerializer
+from utils.api import APIView, IDOnlySerializer, validate_serializer
 
 from .models import Announcement
-from .serializers import (CreateAnnouncementSerializer, AnnouncementSerializer,
+from .serializers import (AnnouncementSerializer, CreateAnnouncementSerializer,
                           EditAnnouncementSerializer)
 
 
diff --git a/conf/serializers.py b/conf/serializers.py
index 693c11ea..f4025cca 100644
--- a/conf/serializers.py
+++ b/conf/serializers.py
@@ -1,6 +1,6 @@
-from utils.api import serializers, DateTimeTZField
+from utils.api import DateTimeTZField, serializers
 
-from .models import SMTPConfig, WebsiteConfig, JudgeServer
+from .models import JudgeServer, SMTPConfig, WebsiteConfig
 
 
 class EditSMTPConfigSerializer(serializers.Serializer):
diff --git a/conf/tests.py b/conf/tests.py
index 647d9448..c526489c 100644
--- a/conf/tests.py
+++ b/conf/tests.py
@@ -1,7 +1,8 @@
 import hashlib
 
 from utils.api.tests import APITestCase
-from .models import SMTPConfig, JudgeServerToken, JudgeServer
+
+from .models import JudgeServer, JudgeServerToken, SMTPConfig
 
 
 class SMTPConfigTest(APITestCase):
diff --git a/conf/urls/admin.py b/conf/urls/admin.py
index daecea22..dcb5c6fc 100644
--- a/conf/urls/admin.py
+++ b/conf/urls/admin.py
@@ -1,6 +1,6 @@
 from django.conf.urls import url
 
-from ..views import WebsiteConfigAPI, SMTPAPI, JudgeServerAPI
+from ..views import SMTPAPI, JudgeServerAPI, WebsiteConfigAPI
 
 urlpatterns = [
     url(r"^smtp$", SMTPAPI.as_view(), name="smtp_admin_api"),
diff --git a/conf/urls/oj.py b/conf/urls/oj.py
index 47a8dd89..db3ede37 100644
--- a/conf/urls/oj.py
+++ b/conf/urls/oj.py
@@ -1,7 +1,6 @@
 from django.conf.urls import url
 
-from ..views import WebsiteConfigAPI, JudgeServerHeartbeatAPI
-
+from ..views import JudgeServerHeartbeatAPI, WebsiteConfigAPI
 
 urlpatterns = [
     url(r"^website$", WebsiteConfigAPI.as_view(), name="website_info_api"),
diff --git a/conf/views.py b/conf/views.py
index 5c6be3f0..4e9f12e1 100644
--- a/conf/views.py
+++ b/conf/views.py
@@ -6,11 +6,12 @@ from account.decorators import super_admin_required
 from utils.api import APIView, CSRFExemptAPIView, validate_serializer
 from utils.shortcuts import rand_str
 
-from .models import SMTPConfig, WebsiteConfig, JudgeServer, JudgeServerToken
-from .serializers import (WebsiteConfigSerializer, CreateEditWebsiteConfigSerializer,
+from .models import JudgeServer, JudgeServerToken, SMTPConfig, WebsiteConfig
+from .serializers import (CreateEditWebsiteConfigSerializer,
                           CreateSMTPConfigSerializer, EditSMTPConfigSerializer,
-                          SMTPConfigSerializer, TestSMTPConfigSerializer,
-                          JudgeServerSerializer, JudgeServerHeartbeatSerializer)
+                          JudgeServerHeartbeatSerializer,
+                          JudgeServerSerializer, SMTPConfigSerializer,
+                          TestSMTPConfigSerializer, WebsiteConfigSerializer)
 
 
 class SMTPAPI(APIView):
diff --git a/contest/models.py b/contest/models.py
index e6532b0b..d620a4c2 100644
--- a/contest/models.py
+++ b/contest/models.py
@@ -1,9 +1,9 @@
 from django.db import models
 from django.utils.timezone import now
-from group.models import Group
 from jsonfield import JSONField
 
 from account.models import User
+from group.models import Group
 from problem.models import AbstractProblem
 from utils.models import RichTextField
 
diff --git a/manage.py b/manage.py
index 066fc698..16b46a54 100755
--- a/manage.py
+++ b/manage.py
@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-from __future__ import unicode_literals
 import os
 import sys
 
diff --git a/oj/local_settings.py b/oj/local_settings.py
index e2be1085..b9ad3b05 100644
--- a/oj/local_settings.py
+++ b/oj/local_settings.py
@@ -37,4 +37,3 @@ STATICFILES_DIRS = [os.path.join(BASE_DIR, "frontend/static/"), BASE_DIR]
 
 # 模板文件夹
 OJ_TEMPLATE_DIRS = [os.path.join(BASE_DIR, 'template/src/')]
-
diff --git a/oj/server_settings.py b/oj/server_settings.py
index 9ec8dcfb..304ccb9b 100644
--- a/oj/server_settings.py
+++ b/oj/server_settings.py
@@ -46,5 +46,3 @@ STATICFILES_DIRS = [os.path.join(BASE_DIR, "static/release/")]
 
 # 模板文件夹
 OJ_TEMPLATE_DIRS = [os.path.join(BASE_DIR, 'template/release/')]
-
-
diff --git a/oj/settings.py b/oj/settings.py
index e25edd2a..1ececa5c 100644
--- a/oj/settings.py
+++ b/oj/settings.py
@@ -10,10 +10,11 @@ https://docs.djangoproject.com/en/1.8/topics/settings/
 For the full list of settings and their values, see
 https://docs.djangoproject.com/en/1.8/ref/settings/
 """
-from __future__ import absolute_import
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
 import os
 
+from .custom_settings import *
+
 # 判断运行环境
 ENV = os.environ.get("oj_env", "local")
 
@@ -22,7 +23,6 @@ if ENV == "local":
 elif ENV == "server":
     from .server_settings import *
 
-from .custom_settings import *
 
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
diff --git a/problem/models.py b/problem/models.py
index 97d623b9..072abec7 100644
--- a/problem/models.py
+++ b/problem/models.py
@@ -1,7 +1,5 @@
-from __future__ import unicode_literals
-
-from jsonfield import JSONField
 from django.db import models
+from jsonfield import JSONField
 
 from account.models import User
 from utils.models import RichTextField
diff --git a/utils/api/_serializers.py b/utils/api/_serializers.py
index 3e887873..7ad87dea 100644
--- a/utils/api/_serializers.py
+++ b/utils/api/_serializers.py
@@ -1,7 +1,6 @@
 import json
 
 from django.utils import timezone
-
 from rest_framework import serializers
 
 
diff --git a/utils/api/api.py b/utils/api/api.py
index 5141a872..bb8ce8cb 100644
--- a/utils/api/api.py
+++ b/utils/api/api.py
@@ -1,13 +1,12 @@
+import functools
 import json
 import logging
-import functools
 
 from django.http import HttpResponse, QueryDict
 from django.utils.decorators import method_decorator
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import View
 
-
 logger = logging.getLogger(__name__)
 
 
diff --git a/utils/api/tests.py b/utils/api/tests.py
index 5ff30f85..50b12c78 100644
--- a/utils/api/tests.py
+++ b/utils/api/tests.py
@@ -1,9 +1,8 @@
-from django.test.testcases import TestCase
 from django.core.urlresolvers import reverse
-
+from django.test.testcases import TestCase
 from rest_framework.test import APIClient
 
-from account.models import User, AdminType
+from account.models import AdminType, User
 
 
 class APITestCase(TestCase):
diff --git a/utils/management/commands/initadmin.py b/utils/management/commands/initadmin.py
index d3e93afc..e33359e8 100644
--- a/utils/management/commands/initadmin.py
+++ b/utils/management/commands/initadmin.py
@@ -1,6 +1,7 @@
 from django.core.management.base import BaseCommand
-from account.models import User, UserProfile, AdminType
-from utils.shortcuts import rand_str
+
+from account.models import AdminType, User, UserProfile
+from utils.shortcuts import rand_str  # NOQA
 
 
 class Command(BaseCommand):
diff --git a/utils/shortcuts.py b/utils/shortcuts.py
index c1ad448b..1dd88342 100644
--- a/utils/shortcuts.py
+++ b/utils/shortcuts.py
@@ -3,7 +3,6 @@ import random
 
 from django.utils.crypto import get_random_string
 
-
 logger = logging.getLogger(__name__)