diff --git a/.gitignore b/.gitignore
index 9c033465..eeec9ee7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,8 @@
 # IDE
 .vscode
 .idea
+*.wpr
+*.wpu
 
 # Temp
 build
diff --git a/.pylintrc b/.pylintrc
index 31be539b..dfa488fb 100644
--- a/.pylintrc
+++ b/.pylintrc
@@ -139,7 +139,7 @@ bad-names=foo,
           tata
 
 # Naming style matching correct class attribute names.
-class-attribute-naming-style=camelCase
+class-attribute-naming-style=snake_case
 
 # Regular expression matching correct class attribute names. Overrides class-
 # attribute-naming-style.
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 00000000..c212511b
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,2 @@
+pyqt
+qdarkstyle
\ No newline at end of file
diff --git a/vnpy/event/__init__.py b/vnpy/event/__init__.py
index d1f08b68..db211d01 100644
--- a/vnpy/event/__init__.py
+++ b/vnpy/event/__init__.py
@@ -1 +1 @@
-from engine import Event, EventEngine, EVENT_TIMER
\ No newline at end of file
+from .engine import Event, EventEngine, EVENT_TIMER
\ No newline at end of file
diff --git a/vnpy/event/engine.py b/vnpy/event/engine.py
index 625c6222..c90dc412 100644
--- a/vnpy/event/engine.py
+++ b/vnpy/event/engine.py
@@ -1,3 +1,7 @@
+"""
+Event-driven framework of vn.py framework.
+"""
+
 from queue import Queue, Empty
 from threading import Thread, Timer
 from collections import defaultdict
diff --git a/vnpy/trader/constant.py b/vnpy/trader/constant.py
new file mode 100644
index 00000000..cd1e53e3
--- /dev/null
+++ b/vnpy/trader/constant.py
@@ -0,0 +1,55 @@
+"""
+General constant string used in VN Trader.
+"""
+
+DIRECTION_LONG = '多'
+DIRECTION_SHORT = '空'
+DIRECTION_NET = '净'
+
+OFFSET_OPEN = '开'
+OFFSET_CLOSE = '平'
+OFFSET_CLOSETODAY = '平今'
+OFFSET_CLOSEYESTERDAY = '平昨'
+
+STATUS_SUBMITTING = '提交中'
+STATUS_NOTTRADED = '未成交'
+STATUS_PARTTRADED = '部分成交'
+STATUS_ALLTRADED = '全部成交'
+STATUS_CANCELLED = '已撤销'
+STATUS_REJECTED = '拒单'
+
+PRODUCT_EQUITY = '股票'
+PRODUCT_FUTURES = '期货'
+PRODUCT_OPTION = '期权'
+PRODUCT_INDEX = '指数'
+PRODUCT_FOREX = '外汇'
+PRODUCT_SPOT = '现货'
+
+PRICETYPE_LIMIT = '限价'
+PRICETYPE_MARKET = '市价'
+PRICETYPE_FAK = 'FAK'
+PRICETYPE_FOK = 'FOK'
+
+OPTION_CALL = '看涨期权'
+OPTION_PUT = '看跌期权'
+
+EXCHANGE_SSE = 'SSE'
+EXCHANGE_SZSE = 'SZSE'
+EXCHANGE_CFFEX = 'CFFEX'
+EXCHANGE_SHFE = 'SHFE'
+EXCHANGE_CZCE = 'CZCE'
+EXCHANGE_DCE = 'DCE'
+EXCHANGE_INE = 'INE'
+EXCHANGE_SGE = 'SGE'
+
+CURRENCY_USD = 'USD'
+CURRENCY_HKD = 'HKD'
+
+INTERVAL_1M = '1分钟'
+INTERVAL_5M = '5分钟'
+INTERVAL_15M = '15分钟'
+INTERVAL_30M = '30分钟'
+INTERVAL_1H = '1小时'
+INTERVAL_4H = '4小时'
+INTERVAL_DAILY = '日线'
+INTERVAL_WEEKLY = '周线'
\ No newline at end of file