Pip2.7尝试从python3库中查找包

Question

我想用pip2.7安装gym库，但它抱怨说该库安装在Python3.5文件夹中。你知道吗

pip2 install gym

结果：

Requirement already satisfied: gym in /home/alex/anaconda2/envs/gym/lib/python3.5/site-packages
Requirement already satisfied: six in /home/alex/anaconda2/envs/gym/lib/python3.5/site-packages (from gym)
Requirement already satisfied: requests>=2.0 in /home/alex/anaconda2/envs/gym/lib/python3.5/site-packages (from gym)
Requirement already satisfied: numpy>=1.10.4 in /home/alex/anaconda2/envs/gym/lib/python3.5/site-packages (from gym)
Requirement already satisfied: pyglet>=1.2.0 in /home/alex/anaconda2/envs/gym/lib/python3.5/site-packages (from gym)

为什么会这样？你知道吗

python -c "import sys; print(sys.path)"给出

['', '/home/alex/naoqi/pynaoqi-python2.7-2.1.4.13-linux64', '/home/alex/naoqi/pynaoqi-python2.7-2.1.2.17-linux64', '/opt/ros/indigo/lib/python2.7/dist-packages', '/home/alex/anaconda2/envs/gym/lib/python35.zip', '/home/alex/anaconda2/envs/gym/lib/python3.5', '/home/alex/anaconda2/envs/gym/lib/python3.5/plat-linux', '/home/alex/anaconda2/envs/gym/lib/python3.5/lib-dynload', '/home/alex/anaconda2/envs/gym/lib/python3.5/site-packages', '/home/alex/anaconda2/envs/gym/lib/python3.5/site-packages/Sphinx-1.4.6-py3.5.egg', '/home/alex/anaconda2/envs/gym/lib/python3.5/site-packages/setuptools-27.2.0-py3.5.egg']