代码同时兼容 python 2.7 和 python 3

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

# python2 中定义普通字符将自动识别为unicode,要放到文件开头
from __future__ import unicode_literals

try:#python2
    from UserDict import UserDict
    #建议按照python3的名字进行import
    from UserDict import DictMixin as MutableMapping
except ImportError:#python3
    from collections import UserDict
    from collections import MutableMapping


# 解析 ini
try:
   import ConfigParser as configparser
except ImportError:
   import configparser


# 打印某个变量的写法
print("ENDPOINT: {} ".format(ENDPOINT))

#报错： TypeError: cannot use a string pattern on a bytes-like object
s = s.decode('utf8')

说明：

1. 关于版本：2.6 版本太老，已被淘汰。2.7 属于过渡版本， 3.x 则属于未来。
2. 3.6 的性能不错，同时还增加了原生的异步库 asyncio ，值得研究。
3. 3.0 里面，把 print 改成了函数，要注意。
4. http url lib 推荐使用 urllib 和 requests 。
5. 升级版本
   CentOS 6 自带 python 2.6，如果升级到 2.7，可能会引起某些系统组件依赖问题。
   CentOS 6 安装 python 3.6, 对系统基本无影响，比升级到 python 2.7 ，对系统影响最小。

python=3.6.8
test -f Python-${python}.tar.xz || wget -c https://www.python.org/ftp/python/${python}/Python-${python}.tar.xz
tar Jxf Python-${python}.tar.xz
cd Python-${python}
EXTRATESTOPTS=--list-tests
./configure --enable-optimizations --prefix=/usr/local
make -j8
sudo make install 

CentOS 7 的 epel 仓库，可以安装

yum install -y python36-devel python36-setuptools 
easy_install-3.6 pip
ln -s /bin/python3.6 /bin/python3

6. python 3 常用的库, 安装的目录在 /usr/local/lib/3.6

pip3 install -U httpie requests mongo redis psutil pymysql stomp.py python3-memcached  virtualenv paramiko sh pycurl ipython pyyaml httpie mysqlclient pymemcache cx_Oracle

7. 制作 RPM 包

APP=python36
VERSION=3.6.8
PREFIX=/usr/local
fpm -s dir -t rpm -n ${APP} -v ${VERSION} --epoch 0 --rpm-user=root \
-p ${APP}-${VERSION}.rpm \
$PREFIX/bin/2to3 $PREFIX/bin/idle3 $PREFIX/bin/pip3 $PREFIX/bin/pydoc3 \
$PREFIX/bin/python3 $PREFIX/bin/python3-config  $PREFIX/bin/pyvenv \
$PREFIX/bin/*3.6  $PREFIX/include/python3.6m \
$PREFIX/lib/libpython3.6m.a $PREFIX/lib/python3.6 $PREFIX/lib/pkgconfig/python-3*.pc \
$PREFIX/lib/pkgconfig/python3*.pc $PREFIX/share/man/man1/python3.*



8. CentOS 7 安装 python 3.10.4

注意：在 gcc 低版本(<8.1.0)下, ./configure 不能增加参数 --enable-optimizations，
否则会报 Could not import runpy module 错误，编译失败.
注意: 自带的openssl 1.0.2版本太低，需要安装epel 的 openssl11 版本，不安装的话编译后的python不支持 ssl 。
 
yum install epel-release
yum install gcc make zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel openssl11-devel 

python=3.10.4
test -f Python-${python}.tar.xz || wget -c https://www.python.org/ftp/python/${python}/Python-${python}.tar.xz
tar Jxf Python-${python}.tar.xz
cd Python-${python}
sed -i 's/PKG_CONFIG openssl /PKG_CONFIG openssl11 /g' configure
./configure && make clean && make -j8 && sudo make altinstall
pip3.10 install requests

nfpm-python3.10.yml
---
name: "python3"
arch: "x86_64"
platform: "linux"
version: "3.10.4"
section: "default"
priority: "extra"
maintainer: "maintainer"
description: |
  python3.
vendor: "vendor"
license: "MIT"
contents:
- src: /usr/local/bin/*3.10*
  dst: /usr/local/bin/
- src: /usr/local/lib/python3.10/*
  dst: /usr/local/lib/python3.10/
- src: /usr/local/lib/libpython3.10.a
  dst: /usr/local/lib/libpython3.10.a
- src: /usr/local/lib/pkgconfig/python-3.10*
  dst: /usr/local/lib/pkgconfig/  
- src: /usr/local/include/python3.10/*
  dst: /usr/local/include/python3.10/
- src: /usr/local/bin/python3.10
  dst: /usr/local/bin/python3
  type: symlink
replaces:
  - python3-libs
  - python3-pip
  - python3-setuptools
depends:
  - openssl-devel
  - libffi-devel
  - zlib-devel
  - bzip2-devel
  - ncurses-devel
  - sqlite-devel 


nfpm package -p rpm -f nfpm-python3.10.yml

yum install python3-3.10.4*.rpm


# CentOS 8 及以上安装 python 3.10.4
yum install openssl-devel  guile
./configure  --enable-optimizations && make clean && make -j8 && sudo make altinstall
pip3.10 install requests

参考：

http://python.jobbole.com/83987/