The simples way you can do this is to use the check_procs sctipt that you can find in nagios-plugins package.

The following command will let you know if the python module '' is running.

/usr/lib/nagios/plugins/check_procs -c 1:1 -a -C python

The -c argument lets you set the critical range. 1:1 will trigger a critical status if there is more or less than 1 process that matches running.

The -a argument will filter based on processes that contain the args ''

The -C argument will make sure that the process is a python process

You can create a command definition to use the check across you nagios installation. Mine looks like this:

# 'check_single_proc' command definition
define command{
    command_name    check_single_proc
    command_line    /usr/lib/nagios/plugins/check_procs -C $ARG1$ -a $ARG2$ -c 1:1

Last thing is to create service definition.

define service {
    use                     generic-service
    host_name               server_hostname
    check_command           check_single_proc!python!


And you are done.

REFERENCE: check_procs plugin manpage