CentOS7 升级 python3 过

检查当前的版本
[root@node1 ~]# python -V
Python 2.7.5
创建安装目录（自定义）
[root@node1 Python-3.7.1]# mkdir /usr/local/python3

从官网下载python3的压缩包，解压（以3.7.1版本为例）
# wget https://www.python.org/ftp/python/3.7.1/Python-3.7.1.tgz
# tar zxf Python-3.7.1.tgz 

cd 进入解压目录，然后
# cd Python-3.7.1
# ./configure --prefix=/usr/local/python3/
# make && make install

cd 进入/usr/bin
其中有python、python2、python2.7三个文件依次指向后者。
备份当前默认版本python，如果有需要还可还原：
# sudo mv python python.bak

创建python3.7的新链接（也可建立python3命令以区分，同mac），这样默认的python版本就替换为python3.7了
# ln -s /usr/local/python3/bin/python3.7 /usr/bin/python

检查当前默认python版本
# python -v

由于yum使用python2，替换为python3后无法正常工作，
因此修改yum配置文件:
# sudo vi /usr/bin/yum
将第一行指定的python版本改为python2.7:
*#!/usr/bin/python 改为 #!/usr/bin/python2.7

修改urlgrabber配置文件（网上很多教程都漏了这一步）
# sudo vi /usr/libexec/urlgrabber-ext-down
同yum，把头部的python改成python2.7

链接：https://www.jianshu.com/p/74227d7ae6a6

例如这样： 

pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available. 

Collecting xxx 

Could not fetch URL <https://pypi.python.org/simple/xxxx/>: There was a problem confirming the ssl certificate: Can’t connect to HTTPS URL because the SSL module is not available. - skipping 

Could not find a version that satisfies the requirement xxx (from versions: ) 

No matching distribution found for xxx

Socket module helper for socket(2)

_socket socketmodule.c timemodule.c

Socket module helper for SSL support; you must comment out the other

socket line above, and possibly edit the SSL variable:

SSL=/usr/local/ssl

_ssl _ssl.c \

-DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \

-L$(SSL)/lib -lssl -lcrypto