EPICS Re: a simple question about pyepics

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Hi,

Note epics.ca.find_libca() is just trying to find a regular dynicamic library, not one defining a Python module. So, in this case you either (assuming Linux):

have it in a directory accessible by any normal program (eg. can you run "caget" from the command line?)
have it in a directory included in your LD_LIBRARY_PATH (same as before, but defined in your environment, instead of in the /etc/ld.conf* files)
have the path to the library declared as PYEPICS_LIBCA

Any of thoe should work, from more general to more specific.

Now, the message you're getting ("cannot connect to lyx:ai3") seems to be consistent with CA not reaching the PV, so maybe:

EPICS_CA_ADDR_LIST is not defined correctly in the environment where you're running Python
The IOC is not accessible for some reason
lyx:ai3 does not exist? (typo??)

Cheers,

Ricardo

On Sat, Aug 18, 2018 at 6:14 PM 梁雅翔 <[email protected]> wrote:

Hi all,

    My environment: CentOS 7（64），epics 3.15.5, python 2.7.5, pyepics from pip.

I could not connect the pv when I using pyepics ( I set the EPICS_BASE,EPICS_HOST_ARCH, PYEPICS_LIBCA ).

    First I started the example IOC, and it worked fine.

    Then I try to connect it using pyepics.

Then I got these:

***************

>>> import epics
>>> from epics import caget, caput
>>> m1 = caget('lyx:ai3')
print m1
cannot connect to lyx:ai3
>>> print m1

      I think maybe the question was installation. Since I didn't understand these sentences well in document of pyepics.

************ sentence in document **************************

Getting Started, Setting up the Epics Environment

Put the dynamic library somewhere in the Python path. A convenient place might be the same site-packages/pyepics library folder as the python package is installed.
To find out which CA library will be used by pyepics, use:
>>> import epics >>> epics.ca.find_libca() 
************************************

      I knew where the libcaI is. But I didn't know where I should put it in python path. So I did not put the libca.so in python path.

     And others was fine. For python I knew such a little thing.

     Could someone give me some help. Why I could not connect it.

Thanks.

Liang yx

Subject:	Re: a simple question about pyepics
From:	Ricardo Cardenes via Tech-talk <[email protected]>
To:	[email protected]
Cc:	Talk EPICS Tech <[email protected]>
Date:	Tue, 21 Aug 2018 05:02:08 -1000

Experimental Physics and Industrial Control System

Getting Started, Setting up the Epics Environment