why does the script doesn't run as source but run as python?

[machineA tmp]# service puppet status
puppet is stopped
[machineA tmp]# /etc/cron.daily/ensure_puppet
[machineA tmp]# service puppet status
puppet is stopped
[machineA tmp]# python /etc/cron.daily/ensure_puppet
Starting puppet agent:                                     [  OK  ]
[machineA tmp]# service puppet status
puppet (pid  16378) is running...

#!/usr/bin/python
import platform
import os
import commands

def chkrun():
    output = commands.getoutput('ps -A')
    if 'puppet' in output:
        return 1 #running
    else:
        return 0 #not running

def run():
    if chkrun() == 0:
        if platform.dist()[1][0] == '7':
            os.system("/usr/sbin/service puppet start")
        else:
            os.system("/sbin/service puppet start")

run()