在准备安装python3和pip3时，请先安装依赖环境：yum install -y libffi-devel，和 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一定要先装！不然会出现如下例一连串连锁反应的bug
在安装linux的centos里安装python3报错：
File "/usr/local/src/Python-3.7.0/Lib/ctypes/__init__.py", line 7, in <module>
from _ctypes import Union, Structure, Array
ModuleNotFoundError: No module named ‘_ctypes‘
make: *** [install] Error 1
踩坑踩得我不要不要的，此处报错，是没有安装依赖环境yum install -y libffi-devel导致，若此处报错，你的stuptools,pip 都安装不上，正确姿势应该是这样
Looking in links: /tmp/tmplw5bl0fh
Collecting setuptools
Collecting pip
Installing collected packages: setuptools, pip
Successfully installed pip-19.0.3 setuptools-40.8.0
pip需要用的环境: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，不安装软连接无法添加，即便添加了也是2.7的版本
另外当你在安装python3时报上面的错，你再去安装yum install -y libffi-devel，会报找不到python这个文件夹，因为你用mv python python.bak 命令备份并且将其删除了，所以，你需要先将python恢复。
这里附上恢复python作者文章地址 https://www.cnblogs.com/sueyyyy/p/10410832.html
安装python3和pip3的作者地址：https://www.cnblogs.com/yoyoketang/p/10195102.html
继续踩坑去，感觉后面无数的坑等着我。。。。在心里为自己点无数根蜡，wish yourself luck
