python - ipython complaining about readline

Question

When I install ipython on my osx and run it, I get the following warning:

 /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/
 site-packages/IPython/utils/rlineimpl.py:96:
 RuntimeWarning: Leopard libedit detected - readline will not be wel
 behaved including some crashes on tab completion, and incorrect
 history navigation. It is highly recommended that you install
 readline, which is easy_installable with: 'easy_install readline'

I have have installed readline, and do not use the system python that was originally installed in /Library/Frameworks/Python.framework/Versions/2.7/bin/python$. The /usr/bin/python points to version 2.7 as shown below

uname -a
Darwin macbook.local 10.8.0 Darwin Kernel Version 10.8.0: Tue Jun  7 
16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386

$sudo pip install readline ipython

$ipython --version
0.11

$/usr/bin/python --version # 
Python 2.7.1 

$which python
/Library/Frameworks/Python.framework/Versions/2.7/bin/python

I have read the question in Python sys.path modification not working - I added /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/readline-6.2.1-py2.7.egg-info to the /Library/Frameworks/Python.framework/Versions/2.7/bin/ipython so that it now looks like this: http://pastebin.com/raw.php?i=dVnxufbS

but I cannot figure out why I am getting the following error:

File
"/Library/Frameworks/Python.framework/Versions/2.7/bin/ipython",
line 9
sys.path.insert(0,"/Library/Frameworks/Python.framework/Versions/2.7/lib/
python2.7/site-packages/readline-6.2.1-py2.7.egg-info")

I do not think the above path is an issue, and my goal is to get ipython to working without complaining about readline even though it is installed and imports correctly.

Answer 1

When pip installs readline, it will never be imported, because readline.so goes in site-packages, which ends up behind the libedit System one, located in lib-dynload (OSX Python path order is very odd). easy_install -a readline will actually install usable readline.

So you can either use easy_install, or use pip and muck about with your PYTHONPATH/sys.path (which essentially means: DO NOT USE PIP).

A bit more detail on the IPython list (though there really isn't anything IPython-specific about this issue): http://mail.scipy.org/pipermail/ipython-user/2011-September/008426.html

EDIT: extra note about virtualenv.

There is a bug in virtualenv < 1.8.3, where readline would not be properly staged when you create an env.