系统自带的默认 python 版本是 2.7.3
python -V
Python 2.7.3
但是当安装 python-pip 时，却提示需要安装 2.6：
apt-get install python-pip
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
python-pkg-resources python-setuptools python2.6 python2.6-minimal
Suggested packages:
python-distribute python-distribute-doc python2.6-doc binfmt-support
Recommended packages:
python-dev-all
The following NEW packages will be installed:
python-pip python-pkg-resources python-setuptools python2.6
python2.6-minimal
0 upgraded, 5 newly installed, 0 to remove and 11 not upgraded.
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所以我用了这样的方法：
wget https://bootstrap.pypa.io/ez_setup.py -O - | python
easy_install pip
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