[IPython-dev] iPython binary wheels for OS-X

[Paul Moore]

On 9 December 2013 15:55, Chris Barker - NOAA Federal
<chris.barker at noaa.gov> wrote:
>> What's the reason you can't pip install readline? Is it because pip
>> insists on compiling it?
>
> No--it needs to be compiled either way--but I _think_ the issue is that pip
> and easy_install put packages on sys.path differently. The pop way puts it
> after the existing readline.

easy_install hacks sys.path to put installed packages before the
standard library. That was controversial behaviour at the time it was
implemented, IIRC - Guido specifically did not want to have user
installed packages able to overwrite stdlib behaviour. I don't know if
that position has changed, it's so rarely relevant that I don't think
people care that much (they tend to care more about the nasty pth file
hacks just for their own sake, rather than for the implications :-))

Pip has never implemented path hacks like this, and uses
--single-version-externally-managed which avoids a lot of setuptools'
controversial behaviour.

So, by policy, it's hard to override stdlib modules - even when they
don't work right (which appears to be the issue with readline on OSX,
if I understand the comments in this thread properly). IMO, we'd be a
lot better off readline was split out of the stdlib so that things
like improved OSX support and pyreadline for Windows could be added.
But I doubt that will ever happen :-(

Paul.