[Add] demo_script.py for ScriptTrader

examples/vn_trader/demo_script.py

@@ -0,0 +1,27 @@
+from time import sleep
+from vnpy.app.script_trader import ScriptEngine
+
+
+def run(engine: ScriptEngine):
+    """"""
+    vt_symbols = ["IF1912.CFFEX", "rb2001.SHFE"]
+
+    # 订阅行情
+    engine.subscribe(vt_symbols)
+
+    # 获取合约信息
+    for vt_symbol in vt_symbols:
+        contract = engine.get_contract(vt_symbol)
+        msg = f"合约信息，{contract}"
+        engine.write_log(msg)
+
+    # 持续运行，使用strategy_active来判断是否要退出程序
+    while engine.strategy_active:
+        # 轮询获取行情
+        for vt_symbol in vt_symbols:
+            tick = engine.get_tick(vt_symbol)
+            msg = f"最新行情, {tick}"
+            engine.write_log(msg)
+
+        # 等待3秒进入下一轮
+        sleep(3)