[Tutor] Installing modules with easy_install

[Ray Jones]

On 08/28/2012 12:35 PM, Steven D'Aprano wrote:
> On 29/08/12 03:41, Ray Jones wrote:
>> I'm working on another Python replacement for a Bash script, and I ran
>> into a need for enhanced time zone functions. Following directions I
>> found on a web site, I did the following:
>>
>> # easy_install --upgrade pytz
> [...]
>> Everything I'm reading suggests that now I should have the pytz module
>> available to me. But from iPython:
>
>> ImportError: No module named pytz
>
>
> Any time you get mysterious errors in iPython, or IDLE, or any other
> add-on to Python, it is important to determine whether the problem is
> with Python itself, or the add-on.
>
> In this case, start up the vanilla Python interactive environment by
> entering "python" at the $ prompt, then "import pytz" at the >>> prompt.
>
> If you get an error:
>
> - copy and paste the full traceback
>
> - show us the contents of sys.path
>
>
> You can also determine how many Python installations you have. At the
> bash $ prompt, type:
>
> python TAB TAB
>
> (that is, press the TAB key twice is succession, do not type the
> letters "t" "a" "b")
>
> and your shell will list the possible executable Python's on your
> system. Copy and paste that output.
>
I tried importing the module with each of the three shells that I have
on my system (I think I need to get rid of idle - I never use it
anymore): python, ipython, and idle. None of them recognize the module.

Discovering which python binaries are available shows that I have
/usr/bin/python and /usr/bin/python2.7. /usr/bin/python is a link to
/usr/bin/python2.7.

My sys.path shows the following:

['',
 '',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/pymodules/python2.7/gtk-2.0',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/pymodules/python2.7',
 '/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode',
 '/usr/lib/python2.7/dist-packages/IPython/Extensions',
 u'/home/ray/.ipython']

Aha! The sys path is in /usr/lib but the module was installed in
/usr/local/lib. What's the easiest fix for this? Creating a link to the
module in the OS, or adding (or changing) the sys.path?


Ray