Update bat script.

Author: githubChenchi

set_pythonpath.bat

@@ -0,0 +1,22 @@
+@echo off
+
+set need_set_pythonpath=1
+for %%x in (python.exe) do set python_exe_path=%%~$PATH:x
+for /f "delims=" %%p in ('echo %python_exe_path%\..\lib\site-packages\quecpython') do set quecpython_path=%%~fp
+if "%PYTHONPATH%" == "" (
+    echo The path is not set, will be set now.
+    set PYTHONPATH=%quecpython_path%
+) else (
+    echo %PYTHONPATH% | findstr /C:"%quecpython_path%" > nul
+    if errorlevel 1 (
+        echo The path is not set, will be set now.
+        set PYTHONPATH=%PYTHONPATH%;%quecpython_path%
+    ) else (
+        echo The path is set before, won't be set again.
+        set need_set_pythonpath=0
+    )
+)
+
+if %need_set_pythonpath% == 1 (
+    setx PYTHONPATH %PYTHONPATH%
+)