ubuntu16.04預設安裝python3以上，需要手動安裝2.7。

1、先確保make、gcc、g++已經安裝好，如果沒有則需要先安裝這三個程式，均使用apt-get的方式直接裝；

2、下載python2.7包：

　　wget https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tgz

3、解壓該包：

　　tar -xvf Python-2.7.13.tgz

4、進入該包：

　　cd Python-2.7.13

5、./configure

6、make

7、make install

安裝完畢，如果因為許可權問題失敗，需要加sudo。

1. sudo apt-get install 安裝的package存放在 /
   usr/lib/python2.7/dist-packages目錄中
2. pip 或者 easy_install安裝的package存放在/usr/local/lib/python2.7/dist-packages目錄中
3. 手動從原始碼安裝的package存放在site-packages目錄中

The dist-packages is a Debian-specific convention that is also present in its derivatives, like Ubuntu. Modules are installed to dist-packages when they come from the Debian package manager into this location:

/usr/lib/python2.7/dist-packages

Since easy_install and pip are installed from the package manager, they also use dist-packages, but they put packages here:

/usr/local/lib/python2.7/dist-packages

dist-packages instead of site-packages. Third party Python software installed from Debian packages goes into dist-packages, not site-packages. This is to reduce conflict between the system Python, and any from-source Python build you might install manually.

This means that if you manually install Python from source, it uses the site-packages directory. This allows you to keep the two installations separate, especially since Debian and Ubuntu rely on the system version of Python for many system utilities.

cv2:

pip install opencv-python

import cv2 出問題解決：

sudo ldconfig

http://blog.sina.com.cn/s/blog_4ddef8f80102v57b.html

http://www.cnblogs.com/world-for-gold/p/6837782.html