whindows cmd 下创建不同版本python的虚拟环境；

Microsoft Windows [版本 10.0.17763.1577]
(c) 2018 Microsoft Corporation。保留所有权利。
首先：安装virtualenv
pip install virtualenv
pip install virtualenvwrapper-win
然后：开始创建虚拟环境

1.查看当着的python版本：
C:UsersAdministrator>python 
Python 3.9.0 (tags/v3.9.0:9cf6752, Oct  5 2020, 15:34:40) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> ^Z

2.切换到建立python虚拟环境的路径：
C:UsersAdministrator>F:
F:>cd F:_Work4_pythonpython36venv
3.使用命令建立虚拟环境： virtualenv -p C:ProgramsPythonpython36python.exe venv36 (virtualenv -p + "python解析器在环境变更中的路径" +  "python虚拟环境的名字")
F:_Work4_pythonpython36venv>virtualenv -p C:ProgramsPythonpython36python.exe venv36
created virtual environment CPython3.6.8.final.0-64 in 3209ms
  creator CPython3Windows(dest=F:_Work4_pythonpython36venvvenv36, clear=False, no_vcs_ignore=False, global=False)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=C:UsersAdministratorAppDataLocalpypavirtualenv)
    added seed packages: pip==20.3.1, setuptools==51.0.0, wheel==0.36.1
  activators BashActivator,BatchActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
4.进入建立的虚拟环境：
F:_Work4_pythonpython36venv>cd venv36

F:_Work4_pythonpython36venvvenv36>dir
 驱动器 F 中的卷是 新加卷
 卷的序列号是 6E6C-5054

 F:_Work4_pythonpython36venvvenv36 的目录

2020/12/09  18:01    <DIR>          .
2020/12/09  18:01    <DIR>          ..
2020/12/09  18:01                42 .gitignore
2020/12/09  18:01    <DIR>          Lib
2020/12/09  18:01               300 pyvenv.cfg
2020/12/09  18:01    <DIR>          Scripts
               2 个文件            342 字节
               4 个目录 265,085,833,216 可用字节
5.使用新建立的虚拟环境：
F:_Work4_pythonpython36venvvenv36>Scriptsactivate.bat
6.查看虚拟环境使用的python版本
(venv36) F:_Work4_pythonpython36venvvenv36>python
Python 3.6.8 (tags/v3.6.8:3c6b436a57, Dec 24 2018, 00:16:47) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> ^Z

7.退出虚拟环境：
(venv36) F:_Work4_pythonpython36venvvenv36>Scriptsdeactivate.bat
F:_Work4_pythonpython36venvvenv36>