Converting Bash scripts to Python

This page contains some notes for the users who are converting their Bash script to Python.

User break

In Bash:

# what to do in case of user break:
exitprocedure()
{
 g.remove rast=$TMP1 > /dev/null
}
# shell check for user break (signal list: trap -l)
trap "exitprocedure" 2 3 15

In Python:

import sys
import atexit

import grass.script as grass

def cleanup():
    grass.run_command('g.remove',
                      rast = tmp1)

def main():
    ...
    return 0

if __name__ == "__main__":
    options, flags = grass.parser()
    atexit.register(cleanup)
    sys.exit(main())

Discard warning/error messages

In Bash:

g.remove rast='map' 2>/dev/null

In Python:

import os
import grass.script as grass

nuldev = file(os.devnull, 'w+')
grass.run_command('g.remove', rast = 'map', stderr = nuldev)
nuldev.close()

Note: In GRASS 6.5+ set

export GRASS_MESSAGE_FORMAT=silent (in Bash)

os.environ['GRASS_MESSAGE_FORMAT'] = 'silent' (in Python)