我想使用一些需要Python 2.6的更新软件，我们目前在专用的CentOS服务器上安装了2.4和2.6，如下所示:
$ which python
/usr/local/bin/python
$ which python2.6
/usr/bin/python2.6
$ which python2.4
/usr/local/bin/python2.4
$ ls -l /usr/local/bin/py*
-rwxr-xr-x 1 root root 81 Aug 9 2007 /usr/local/bin/pydoc
-rwxr-xr-x 2 root root 3394082 Aug 9 2007 /usr/local/bin/python
-rwxr-xr-x 2 root root 3394082 Aug 9 2007 /usr/local/bin/python2.4
我如何切换到使用2.6作为默认的python？