1.卸载python2.7

sudo apt-get remove python2.7

2.卸载python2.7及其依赖

sudo apt-get remove --auto-remove python2.7

3.消除python2.7

sudo apt-get purge python2.7 or sudo apt-get purge --auto-remove python2.7

安装python3：

sudo apt-get install python3.8:

安装opencv-python：

pip install opencv-python，结果报错：

No module named 'skbuild'

解决方法：

pip3 install -i https://pypi.tuna.tsinghua.edu.cn/simple scikit-build

安装完成后，再次安装opencv-python发现还会会报错:

Problem with the CMake installation, aborting build. CMake executable is cmake
大致的意思是：CMake安装有问题，正在中止构建。
然后在终端输入：

pip3 install -i https://pypi.tuna.tsinghua.edu.cn/simple cmake

再次尝试，opencv-python安装成功

原文链接：https://blog.csdn.net/weixin_44996884/article/details/108678298

安装pip3遇到报错

下列软件包有未满足的依赖关系：

python3-distutils : 依赖: python3 (< 3.9) 但是 3.9.4-1build1 正要被安装

依赖: python3-lib2to3 (>= 3.6.4) 但是它将不会被安装

先卸载当前python3以及依赖

#卸载python3
apt-get remove python3
#卸载python3及其依赖
apt-get remove --auto-remove python3
#清除python3
apt-get purge python3

重新安装

 apt-get install python3.7

apt-get install python3-distutils

curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py

python3 get-pip.py

centos下安装

1.编译工具的安装

yum -y groupinstall "Development tools"
 
yum -y install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel
 
yum install libffi-devel -y

2 下载python3.7的安装包并解压

mkdir /home/python3.7
cd /home/python3.7
wget https://www.python.org/ftp/python/3.7.0/Python-3.7.0.tar.xz
或者在windows浏览器里打开这个文件，下载完之后，上传到服务器中去（网速会快点）
使用rz命令 上传
tar xvf Python-3.7.0.tar.xz  解压
 3.安装

mkdir /usr/local/python3 #创建编译安装目录
cd Python-3.7.0
./configure --prefix=/usr/local/python3
make && make install

4.创建软链接

ln -s /usr/local/python3/bin/python3 /usr/local/bin/python3
ln -s /usr/local/python3/bin/pip3 /usr/local/bin/pip3

参考：Ubuntu安装Python3 和卸载 - 武老师 - 博客园 

Python3 安装pip 提示ModuleNotFoundError: No module named 'distutils.util' - 周伯通的麦田 - 博客园
centos安装python3.7_风一样的男子&的博客-CSDN博客_centos 安装python3.7
Centos7安装python 3_gslhelloworld的博客-CSDN博客_centos7 yum安装python3

1. 卸载python

rpm -qa|grep python|xargs rpm -e --allmatches --nodeps

whereis python|xargs rm -fr

2. 卸载yum

rpm -qa|grep yum|xargs rpm -e --allmatches --nodeps
rm -rf /etc/yum.repos.d/*
whereis yum|xargs rm -fr

3. 重装python2.7

mkdir /usr/local/src/python
cd /usr/local/src/python
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-2.7.5-58.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-pycurl-7.19.0-19.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-devel-2.7.5-58.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-libs-2.7.5-58.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-8.el7.noarch.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-python-4.11.3-25.el7.x86_64.rpm
 
rpm -ivh python-*   rpm-python-*

若在最后一行代码中提示错误：依赖检测失败
解决方法：
命令末尾加上–nodeps --force

4. 安装yum

mkdir /usr/local/src/yum
cd /usr/local/src/yum
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-154.el7.centos.noarch.rpm 
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-42.el7.noarch.rpm
rpm -ivh --force --nodeps yum-*

5. 测试是否安装成功

 yum

6. 遇到There are no enabled repos.的问题
   yum repolist all，显示0
   解决方法：
   查看 网易的《CentOS镜像使用帮助》：http://mirrors.163.com/.help/centos.html
   下载Centos7-Base
   放入/etc/yum.repos.d/

# 清除缓存
yum clean all
# 生成缓存
yum makecache
yum -y update