[FIXED] ipython install new modules

Issue

I am used to the R functionality of installing packages and I am trying to do the same thing with ipython. Sometimes the following method works but then again sometimes it doesn't and I would like to finally find out why it only works half the time.

Normally to install a module (like the requests module for example) I would type the following after opening a fresh terminal:

$ sudo pip install requests
Password: ******* 

This would then be followed by a message indicating that the install was successful or that it has already been installed.

Requirement already satisfied (use --upgrade to upgrade): 
requests in /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
Cleaning up... 

Which suggests that the code can be accessed. And indeed if I run python now from the terminal it shows a good response without any errors whatsoever.

$ python
ActivePython 2.7.2.5 (ActiveState Software Inc.) based on
Python 2.7.2 (default, Jun 24 2011, 12:20:15) 
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import requests
>>> 

I now open PyLab through Alfred and it gives me an error.

Welcome to pylab, a matplotlib-based Python environment [backend: WXAgg].
For more information, type 'help(pylab)'.

In [1]: import requests
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
/Users/vincentwarmerdam/<ipython-input-1-686486c241c8> in <module>()
----> 1 import requests

ImportError: No module named requests

I've read some help from another question on StackOverflow (here) which suggests that I install the module from ipython shell. This gives an even more baffling response:

In [2]: !pip install requests
Requirement already satisfied (use --upgrade to upgrade): requests in     
/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
Cleaning up...

In [3]: import requests
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
/Users/vincentwarmerdam/<ipython-input-3-686486c241c8> in <module>()
----> 1 import requests

ImportError: No module named requests

This seems very strange to me. Are there multiple versions of python installed on the system? How could I check this? Do I need to point ipython to the location of the installed code?

Solution

actually there is a much much much more elegant solution. when pip is installed then within python you can do things like this as well:

import pip

def install(package):
   pip.main(['install', package])

install('requests') 

which is easier. once logged into a virtualenv you can just make sure that you have what you need in the session you are in. easy.

edit

Another alternative would be to use the %%bash magic.

%%bash
pip install requests

edit2

If you want the standard output, one could even use the exclamation bang.

! pip install requests

edit3

From within ipython this is the safest installation method.

%pip install requests

This ensures that everything is installed in the virtualenv that your ipython is installed in.

Answered By - cantdutchthis