1、用pip来使用第3方模块，先安装pip

# 下载安装脚本
$ curl -O https://bootstrap.pypa.io/get-pip.py

# 安装
sudo python3 get-pip.py 

2、安装成功后，查看安装版本，确定与你目前的python3版本一致

 pip3 -V
pip 22.1.2 from /usr/local/lib/python3.8/site-packages/pip (python 3.8)

3、安装virtualenv

pip3 install virtualenv 

4、使用虚拟机环境 

$ cd /var/www/your_project_name

# 创建虚拟环境，其中py-env为你自定义的环境名称
$ virtualenv -p python3 py-env

# 激活虚拟环境
$ source py-env/bin/activate

# 这时命令行路径前面会出现你的虚拟环境名，例如：
(py-env) [root@zjz ~]#

# 查看你目前的插件，有些可能之前系统python环境已经安装了，你可以不用重复安装
 pip3 list

Package    Version
---------- -------
pip        22.1.2
setuptools 62.6.0
wheel      0.37.1

5、安装python模块

pip3 install Flask
Collecting Flask
  Using cached Flask-2.1.2-py3-none-any.whl (95 kB)
Collecting itsdangerous>=2.0
  Using cached itsdangerous-2.1.2-py3-none-any.whl (15 kB)
Collecting Jinja2>=3.0
  Using cached Jinja2-3.1.2-py3-none-any.whl (133 kB)
Collecting click>=8.0
  Using cached click-8.1.3-py3-none-any.whl (96 kB)
Collecting Werkzeug>=2.0
  Using cached Werkzeug-2.1.2-py3-none-any.whl (224 kB)
Collecting importlib-metadata>=3.6.0
  Using cached importlib_metadata-4.12.0-py3-none-any.whl (21 kB)
Collecting zipp>=0.5
  Using cached zipp-3.8.0-py3-none-any.whl (5.4 kB)
Collecting MarkupSafe>=2.0
  Using cached MarkupSafe-2.1.1-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (25 kB)
Installing collected packages: zipp, Werkzeug, MarkupSafe, itsdangerous, click, Jinja2, importlib-metadata, Flask
Successfully installed Flask-2.1.2 Jinja2-3.1.2 MarkupSafe-2.1.1 Werkzeug-2.1.2 click-8.1.3 importlib-metadata-4.12.0 itsdangerous-2.1.2 zipp-3.8.0

6、退出虚拟环境

deactivate