Experimental Physics and
Industrial Control System

John Hammonds <[email protected]> · Wed, 06 Aug 2008 13:50:08 -0500

This should be LD_LIBRARY_PATH. You were able to find epicsCA which is
the Python part of things. libca is the epics library which does not
have anything to do with Python.

Also, for what it is worth, I have also been working to update Geoff
Savage's CaPython. This does not provide quite as slick an interface as
Matt's but it is a pretty full implementation of the Channel Access
Libraries. I have most of this working using a newer version of SWIG
and python. I have not yet added the 3.14 CA calls but it can do things
like deal with larger arrays. I am trying to coordinate with Geoff
before releasing this.
John
Tim Mooney wrote:

Adam,  The first thing I'd try is setting either the LD_LIBRARY_PATH,
or the PYTHONPATH, environment variable to the directory containing the
needed .so file.  E.g.:
setenv LD_LIBRARY_PATH /usr/local/lib/epics/base/lib/linux-x86_64
   or, if you're using bash,
export LD_LIBRARY_PATH=/usr/local/lib/epics/base/lib/linux-x86_64

Adam Kadzban wrote:

Hey all, I'm a relative newcomer to both Linux, Python, and Epics, so
sorry if this has an easy solution. I guess I'm not even sure if
it's a problem with Epics itself, or Python, or something else. I'm
having some problems getting Python to import the EpicsCA module.
I'm running Ubuntu 8.04 (Hardy), and it's an x86_64 system. The
epics base seems to have installed fine, I put it in
/usr/local/lib/epics/base. I got the epics module here
<http://cars9.uchicago.edu/%7Enewville/Epics/Python/>
(http://cars9.uchicago.edu/~newville/Epics/Python/), and again it
looked like it installed fine to /usr/local/EpicsCA-2.1.5.
The problem is, whenever I try to do anything with EpicsCA in Python,
it dies on me because it can't find libca.so. Here's what it shows
when I try to import EpicsCA:
 >>> import EpicsCA

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "/usr/lib/python2.5/site-packages/EpicsCA/__init__.py", line
116, in <module>

import _epics

ImportError: libca.so: cannot open shared object file: No such file
or directory
(it does the same if I try "from EpicsCA import *")
However, I know libca.so exists, it's here:
adam:$ locate libca.so
/usr/local/lib/epics/base/lib/linux-x86_64/libca.so
/usr/local/lib/epics/base/lib/linux-x86_64/libca.so.3.14
/usr/local/lib/epics/base/src/ca/O.linux-x86_64/libca.so.3.14
So there it is, in the epics base folder. Why can't Python find it?
I was digging around online, and found how to add places for Python
looks for modules to import them (though I don't think that's the
problem, because it can't find libca.so, not a module), and I added a
bunch of places, to no avail. Anyone have any ideas?

Not sure if it's relevant, but when I ran the setup.py script to
install EpicsCA, I had to edit the environment variable manually. I
added "EPICS_BASE=/usr/local/lib/epics/base" to /etc/environment, but
for some reason os.environ['EPICS_BASE'] wasn't finding
/usr/local/lib/epics/base. I had to change the setup script to look
there. Though if I opened a Python interpreter and printed
os.environ['EPICS_BASE'], it came out as /usr/local/lib/epics/base.
So something fishy was going on there, not sure if it's related though.

Thanks,
Adam Kadzban

--
John Hammonds
Beamline and Data Acquisition Group
APS Engineering Support Division
Argonne National Laboratory
[email protected] <mailto:[email protected]>
(630)252-5317

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System