python numpy 或 scipy 错误

我想在 python 中工作。当我导入 scipy 或 numpy 时，它会显示以下错误：

saikat@saikat:~/Downloads/Python-2.7.15$ python
Python 2.7.14 |Anaconda, Inc.| (default, Dec  7 2017, 17:05:42) 
[GCC 7.2.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named numpy
>>> 

但是当我使用这个命令时：

sudo pip install numpy scipy

表明：

saikat@saikat:~/Downloads/Python-2.7.15$ sudo pip install numpy scipy
The directory '/home/saikat/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/saikat/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Requirement already satisfied: numpy in /usr/local/lib/python2.7/dist-packages/numpy-1.14.3-py2.7-linux-x86_64.egg (1.14.3)
Requirement already satisfied: scipy in /usr/local/lib/python2.7/dist-packages (1.1.0).

我应该怎么办？