Appion

Mean/std dev filtration is failing with the following error message:
TypeError: unsupported operand type(s) for -: 'str' and 'int'

Here is the complete log:

... Time stamp: 17jul11g14
 ... Function name: stackFilter
 ... Appion directory: /opt/myamisnap/lib
 ... Processing hostname: node22
 ... Using split database
Connected to database: 'nyap_31'
 ... Committing data to database
 ... Run directory: /gpfs/appion/pacharya/17jul10k/stacks/meanfilt868_3
!!! WARNING: directory '/gpfs/appion/pacharya/17jul10k/stacks/meanfilt868_3' already exists.
 ... Writing function log to: stackFilter.log
 ... Uploading ScriptData....
 ... Found 1 processors on this machine
 ... Running Appion version 'trunk'
 ... querying stack particles from stackid=868 at Tue Jul 11 06:14:40 2017
 ... sorting particles
 ... received 128442 stack particles in 33.68 sec
 ... Getting stack data for stackid=868
Old stack info: 'test'
Traceback (most recent call last):
  File "/opt/myamisnap/bin/stackFilter.py", line 103, in <module>
    subStack.start()
  File "/opt/myamisnap/bin/stackFilter.py", line 77, in start
    f.write('%i\n' % partnum-1)
TypeError: unsupported operand type(s) for -: 'str' and 'int'