卸載：
1抹剩、卸載python3.4
sudo apt-get remove python3.4
2遂鹊、卸載python3.4及其依賴
sudo apt-get remove --auto-remove python3.4
3慷蠕、清除python3.4
sudo apt-get purge python3.4
or
sudo apt-get purge --auto-remove python3.4
安裝：
下載python
wget https://www.python.org/ftp/python/2.7.9/Python-2.7.9.tgz
wget -P /usr/lib https://www.python.org/ftp/python/2.7.9/Python-2.7.9.tgz(下載文件到指定目錄)
解壓、編譯安裝
tar -zxvf Python-2.7.9.tgz
cd Python-2.7.9
./configure --prefix=/usr/local/python-2.7.9
make
make install
系統(tǒng)自帶了python版本，我們需要為新安裝的版本添加一個軟鏈
ln -s /usr/local/python-2.7.9/bin/python /usr/bin/python2.7.9
