Debian No Module名为numpy

Question

I've installed Python Numpy on Debian using...

apt-get install python-numpy

But when run the Python shell I get the following...

Python 2.7.10 (default, Sep  9 2015, 20:21:51)
[GCC 4.9.2] 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

When I view the contents of /usr/local/lib/python2.7/site-packages/ I noticed numpy is not list.

If I install it via pip ie pip install numpy it works just fine, However, I want to use the apt-get method. What I'm I doing wrong?

Other:

echo $PYTHONPATH /usr/local/lib/python2.7

dpkg -l python-numpy...

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                            Version                      Architecture                 Description
+++-===============================================-============================-============================-====================================================================================================
ii  python-numpy                                    1:1.8.2-2                    amd64                        Numerical Python adds a fast array facility to the Python language

Python 2.7.10

['', '/usr/local/lib/python2.7', '/usr/local/lib/python27.zip', '/usr/local/lib/python2.7/plat-linux2', '/usr/local/lib/python2.7/lib-tk', '/usr/local/lib/python2.7/lib-old', '/usr/local/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/site-packages']

which -a python...

/usr/local/bin/python
/usr/bin/python

echo $PATH

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Answer 1

As you can tell from your which result, the python you are running when just typing python is /usr/local/bin/python .

It's a python you probably installed there yourself, as Debian will never put anything in /usr/local by itself (except for empty directories).

How? Well, by running pip for instance. As a rule, you should never use pip outside of a virtualenv , because it will install stuff on your system that your package manager will not know about. And maybe break stuff, like what you see on your system.

So, if you run /usr/bin/python , it should see the numpy package you installed using your package manager.

How to fix it? Well, I would clear anything in /usr/local (beware, it will definitely break stuff that rely on things you installed locally). Then I would apt-get install python-virtualenv , and always work with a virtualenv.

$ virtualenv -p /usr/bin/python env
$ . env/bin/activate
(env)$ pip install numpy
(env)$ python
>>> import numpy
>>>

That way, packages will be installed in the env directory. You do all this as a regular user, not root. And your different projects can have different environments with different packages installed.