日前在CentOS上搭建测试环境时候，遇到需要升级python版本的情况，于是就记录了整个升级的过程：
在CentOS5中自带的Python版本是2.4，但是目前许多基于Python的应用软件要求的Python版本应要高于2.4。升级 python版本的时候千万不能卸载python 2.4，再安装python2.7，这样会有无穷无尽的麻烦，保守的方式是直接安装python2.7的源码包，也就是python两个版本共存。（因为 Centos里面有很多程序是依赖着python，所有最好不要尝试去卸载python2.4）。
(1)下载/安装python
下载Python2.7.2.tgz（# wget http://www.python.org/ftp/python/2.7.2/Python-2.7.2.tgz)
- $tar jxvf Python2.7.2.tgz
- $cd Python2.7.2
- $./configure
- $make && make install
自此,python2.7安装后路径默认是在/usr/local/lib/python2.7
查看Python版本：
$ /usr/local/bin/python2.7 -V
(2)建立软连接，使系统默认的python指向python2.7
正常情况下即使python2.7安装成功后，系统默认指向的python仍然是2.4版本，考虑到yum是基于
python2.4才能正常工作，不敢轻易卸载。如何实现将系统默认的python指向到2.7版本呢？
mv /usr/bin/python /usr/bin/python.bak （或者rm -rf /usr/bin/python）
ln -s /usr/local/bin/python2.7 /usr/bin/python
检验python指向是否成功
python -V
(3) 解决系统python软链接指向python2.7版本后，yum不能正常工作
方法：
$vi /usr/bin/yum
将文本编辑显示的第一行
#!/usr/bin/python修改为#!/usr/bin/python2.4，保存修改即可
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安装前确认zlib是否安装？没安装 请yum install zlib zlib-devel
wget http://www.python.org/ftp/python/2.7.3/Python-2.7.3.tgz
tar zxvf Python-2.7.3.tgz
cd Python-2.7.3
./configure --prefix=/usr && make && make install
(也可以考虑不覆盖老版本，自行定义安装路径，最后做软链接)
安装完毕，但会发现CentOS yum需要系统自带的2.4版本，主要一定修改yum，否则会导致yum不能使用。
vi /usr/bin/yum
第1行
#!/usr/bin/python修改为：#!/usr/bin/python2.4
然后安装EasyInstall
wget http://pypi.python.org/packages/2.7/s/setuptools/setuptools-0.6c11-p2y2.7.egg
sh setuptools-0.6c11-p2y2.7.egg
安装完成后就可以直接使用easy_install命令安装第三方Python开发包了，例如：easy_install SQLObject
全部自动完成，不用一个个去找egg了。
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找到问题了原因了，问题已经解决，解决方法如下：
将原来好用的机器上的/usr/lib/python2.4整个目录拷贝到本机的相应路径下，同时，拷贝好用机器上的/usr/bin/python*到本机相应路径下。
#scp -r 192.168.1.2:/usr/lib/python2.4 /usr/lib/
#scp -r 192.168.1.2:/usr/bin/python* /usr/bin/
# vi /etc/profile
添加环境变量
export PATH="/usr/bin/:$PATH"
#source /etc/profile
# python -v 重新导入
出现如下字样，即可正常：
# installing zipimport hook
import zipimport # builtin
# installed zipimport hook
# /usr/lib/python2.4/site.pyc matches /usr/lib/python2.4/site.py
import site # precompiled from /usr/lib/python2.4/site.pyc
# /usr/lib/python2.4/os.pyc matches /usr/lib/python2.4/os.py
import os # precompiled from /usr/lib/python2.4/os.pyc
import posix # builtin
# /usr/lib/python2.4/posixpath.pyc matches /usr/lib/python2.4/posixpath.py
import posixpath # precompiled from /usr/lib/python2.4/posixpath.pyc
# /usr/lib/python2.4/stat.pyc matches /usr/lib/python2.4/stat.py
import stat # precompiled from /usr/lib/python2.4/stat.pyc
import errno # builtin
# /usr/lib/python2.4/UserDict.pyc matches /usr/lib/python2.4/UserDict.py
import UserDict # precompiled from /usr/lib/python2.4/UserDict.pyc
# /usr/lib/python2.4/copy_reg.pyc matches /usr/lib/python2.4/copy_reg.py
import copy_reg # precompiled from /usr/lib/python2.4/copy_reg.pyc
# /usr/lib/python2.4/types.pyc matches /usr/lib/python2.4/types.py
import types # precompiled from /usr/lib/python2.4/types.pyc
import japanese # directory /usr/lib/python2.4/site-packages/japanese
# /usr/lib/python2.4/site-packages/japanese/__init__.pyc matches /usr/lib/python2.4/site-packages/japanese/__init__.py
import japanese # precompiled from /usr/lib/python2.4/site-packages/japanese/__init__.pyc
import japanese.aliases # directory /usr/lib/python2.4/site-packages/japanese/aliases
# /usr/lib/python2.4/site-packages/japanese/aliases/__init__.pyc matches /usr/lib/python2.4/site-packages/japanese/aliases/__init__.py
import japanese.aliases # precompiled from /usr/lib/python2.4/site-packages/japanese/aliases/__init__.pyc
import encodings # directory /usr/lib/python2.4/encodings
# /usr/lib/python2.4/encodings/__init__.pyc matches /usr/lib/python2.4/encodings/__init__.py
import encodings # precompiled from /usr/lib/python2.4/encodings/__init__.pyc
# /usr/lib/python2.4/codecs.pyc matches /usr/lib/python2.4/codecs.py
import codecs # precompiled from /usr/lib/python2.4/codecs.pyc
import _codecs # builtin
# /usr/lib/python2.4/encodings/aliases.pyc matches /usr/lib/python2.4/encodings/aliases.py
import encodings.aliases # precompiled from /usr/lib/python2.4/encodings/aliases.pyc
# /usr/lib/python2.4/warnings.pyc matches /usr/lib/python2.4/warnings.py
import warnings # precompiled from /usr/lib/python2.4/warnings.pyc
# /usr/lib/python2.4/linecache.pyc matches /usr/lib/python2.4/linecache.py
import linecache # precompiled from /usr/lib/python2.4/linecache.pyc
# /usr/lib/python2.4/encodings/utf_8.pyc matches /usr/lib/python2.4/encodings/utf_8.py
import encodings.utf_8 # precompiled from /usr/lib/python2.4/encodings/utf_8.pyc
Python 2.4.3 (#1, Sep 3 2009, 15:37:12)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-46)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
dlopen("/usr/lib/python2.4/lib-dynload/readline.so", 2);
import readline # dynamically loaded from /usr/lib/python2.4/lib-dynload/readline.so
>>>
# python
Python 2.4.3 (#1, Sep 3 2009, 15:37:12)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-46)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
现在，终于找回久违的python2.4.3了，再执行yum安装一个包试试。
# yum install rrdtool
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* addons: centos.tt.co.kr
* base: ftp.cse.yzu.edu.tw
* extras: centos.tt.co.kr
* updates: data.nicehosting.co.kr
addons | 951 B 00:00
一切ok了。
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