Re: [HTCondor-users] proper way to check fo undefined classAd in python

[John M Knoeller <johnkn@xxxxxxxxxxx>]

!= should never have worked to compare undefined.  So if this used to work in the python bindings that was a bug. 

Undefined is not like other values, it cannot be compared using == or !=, it can only be compared using the exact equality (is or =?=)  or exact inequality (isnt or =!=) operators

-tj

-----Original Message-----
From: HTCondor-users <htcondor-users-bounces@xxxxxxxxxxx> On Behalf Of Stefano Belforte
Sent: Tuesday, June 21, 2022 12:17 PM
To: HTCondor-Users Mail List <htcondor-users@xxxxxxxxxxx>
Subject: [HTCondor-users] proper way to check fo undefined classAd in python

Hi experts !
I need to know what is the proper way to check if a classAd is Undefined
when using HTCondor python bindings.
Longish story short (check [1] if you care for context and details) :
I have some oldish python script which uses

import classad
.. get some classAd list via querying schedd via condor bindings...
   if someAd != classad.Value.Undefined:
     blah blah

and I found that it does not work anymore (new HTCondor release ?
I am running that with 9.2.0 atm) move to python3 ? It is a tiny corner
of our phase space and it went un-noticed for who knows how long).

Instead this works:
   if someAd is not classad.Value.

does nor work means that the output of someAd != classad.Value.Undefined
is not a boolean any more, with python debugger:
(Pdb) ad['CRAB_UserGroup'] != classad.Value.Undefined
undefined != undefined

Yes, I can replace "!=" with "is not", no problem, it works for me now,
but I need to know if this works by accident (like the previous way ? not
my code, do not shoot the messenger), or if it is the correct syntax
and will work forever. Or what is otherwise your recommendation.

I looked in https://htcondor.readthedocs.io/en/latest/apis/python-bindings/api/classad.html
but could not find this information (does not mean that it is not there, of course).

Thanks

Stefano



[1]
https://github.com/dmwm/CRABServer/issues/7288
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