On Thu, Sep 25, 2014 at 9:00 AM, Donald Stufft <donald@stufft.io> wrote:
1) Just always default to —user and add a —system or similar flag, this
    is super easy to change but is a backwards incompatible change and
    would need to go through a deprecation window.

Maybe would have been the way to go to begin with, but I think backwards compatibility should probably trump "better" -- even with a deprecation window.
 
2) Switch to —user based on if the user has permission to write to the
    site-packages or not.

ouch -- no. Why not a clear error message if pip can't write to site-packages -- something like:

"""
pip doesn't have permissions to write to the system location. If you want to install this package system-wide, you need to run pip with admin priviledges (and example here if it's easy), if you want to install for this user only, pass the "--user" flag to pip install
""" 

"In the face of ambiguity, refuse the temptation to guess."

-Chris

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