Win10 修改環境變數，不用重啟或登出賬號；只需每次執行Python前管理員許可權執行bat，修改環境變數，重新開啟cmd即可立即切換python。方法：

1. Python多版本安裝目錄儘量在一起，比如：

1. 系統變數PATH裡新增python路徑"%WhichPython%"和"%WhichPython%\Scripts\";另外新增WhichPython變數，值設為某個python路徑，比如：C:\Users\laoya\AppData\Local\Programs\Python\Python37

2.管理員執行bat指令碼，輸入1/2/3，即可切換

@echo off
%1 mshta vbscript:CreateObject("Shell.Application").ShellExecute("cmd.exe","/c %~s0 ::","","runas",1)(window.close)&&exit
choice /c 123 /m "Python27->Press 1,Python35->Press 2,Python37->Press 3"
if errorlevel 3 goto Python37
if errorlevel 2 goto Python35
if errorlevel 1 goto Python27

:Python27
setx WhichPython C:\Users\laoya\AppData\Local\Programs\Python\Python27 /M
goto end

:Python35
setx WhichPython C:\Users\laoya\AppData\Local\Programs\Python\Python35 /M
goto end

:Python37
setx WhichPython C:\Users\laoya\AppData\Local\Programs\Python\Python37 /M
goto end

:end
echo GoodBye