1. 安装依赖关系
yum -y install gcc python36-devel bzip2-devel sqlite-devel openssl-devel readline-devel xz-devel xz-devel tk-devel gdbm-devel libffi-devel

2. 下载和安装python包

cd /usr/local/src

wget ​​​https://www.python.org/ftp/python/3.9.5/Python-3.9.5.tgz​​​
tar zxvf Python-3.9.5.tgz

cd Python-3.9.5/

./configure --prefix=/usr/local/python3.9 --with-ssl

make && make install
3. 修改软连接
  1. ln -fs /usr/local/python3.9/bin/python3.9 /usr/bin/python
    
ln -fs /usr/local/python3.9/bin/python3.9 /usr/bin/python3
    
ln -fs /usr/local/python3.9/bin/pip3.9 /usr/bin/pip
    
ln -fs /usr/local/python3.9/bin/pip3.9 /usr/bin/pip3
5.修改yum文件
  1. vi /usr/bin/yum
    vi /usr/libexec/urlgrabber-ext-down
第一行改都修改为: (原因是安装了python3.8,CentOS 7.X 自带的yum采用的是python2.X，当系统将python升级到2.7 或3.X后，出现语法解释错误)
  2. #!/usr/bin/python2.7

6.升级pip
  1. python -m pip install --upgrade pip
出现错误必须：
ln -fs /usr/local/python3.9/bin/python3.9 /usr/bin/python
ln -fs /usr/local/python3.9/bin/python3.9 /usr/bin/python3
ln -fs /usr/local/python3.9/bin/pip3.9 /usr/bin/pip
ln -fs /usr/local/python3.9/bin/pip3.9 /usr/bin/pip3
 
必须
 
# 顺手解决 Can't locate Tcl/Tk libs and/or headers
sudo yum install tcl-devel tk-devel
# 解决_ssl问题
sudo yum install openssl-devel

网上的加什么网关方法都是不行的记住了，忙了半个小时