unable to toggle machine power by python interface

>>> import linuxcnc
>>> c = linuxcnc.command()
>>> c.state(linuxcnc.STATE_ESTOP_RESET)
>>> c.state(linuxcnc.STATE_ON)
>>> s = linuxcnc.stat()
>>> s.poll()
>>> task_state = getattr(s, 'task_state' )
>>> print task_state
4

import linuxcnc
import numpy as np

if __name__ == '__main__':
    try:

        e = linuxcnc.error_channel()
        s = linuxcnc.stat() # create a connection to the status channel
        s.poll() # get current values        
        c = linuxcnc.command()
        c.wait_complete() # wait until mode switch executed
        
        c.reset_interpreter() 
        c.teleop_enable(1)
        c.wait_complete() # wait until mode switch executed        
        
        task_state = getattr(s, 'task_state' )
        task_mode = getattr(s, 'task_mode' )    
        homed =  getattr(s, 'homed' )
        current_line =  getattr(s, 'motion_line' )
##        motion_mode =  getattr(s, 'motion_mode' )
        motion_type  =  getattr(s, 'motion_type' )            
        paused =  getattr(s, 'paused' ) 
        print 'task_state',task_state,'task_mode',task_mode, 'homed',homed
        print 'current_line',current_line,'paused',paused    

        if task_state != linuxcnc.STATE_ON :
            c.state(linuxcnc.STATE_ESTOP_RESET)            
            c.state(linuxcnc.STATE_ON) #
            c.wait_complete() # wait until mode switch executed
            s.poll() # get current values
            task_state = getattr(s, 'task_state' )            
            print 'state changed to', task_state 

        if np.sum(homed)<4:
            if  task_mode !=linuxcnc.MODE_MANUAL : #(MODE_MDI, MODE_MANUAL, MODE_AUTO). 
                c.mode(linuxcnc.MODE_MANUAL )     #linuxcnc.MODE_AUTO
                c.wait_complete() # wait until mode switch executed
            c.home(0)
            c.wait_complete() # wait until mode switch executed            
            c.home(1)
            c.wait_complete() # wait until mode switch executed            
            c.home(2)
            c.wait_complete() # wait until mode switch executed            
            c.home(3)
            c.wait_complete() # wait until mode switch executed
            s.poll() # get current values
            homed =  getattr(s, 'homed' )            
            print 'homed',  homed

        if  task_mode !=linuxcnc.MODE_AUTO: #(MODE_MDI, MODE_MANUAL, MODE_AUTO).
            c.mode(linuxcnc.MODE_AUTO)     #linuxcnc.MODE_AUTO
            c.wait_complete() # wait until mode switch executed
            s.poll() # get current values
            task_mode = getattr(s, 'task_mode' )              
            print 'mode changed to', task_mode
            
        print 'working'
        c.abort()
        c.reset_interpreter()         
        c.program_open("/home/sam3/linuxcnc/NGC_file/fur_cut1.ngc")
        c.auto(linuxcnc.AUTO_RUN, 0)

        flag = 0
        while 1:
            error = e.poll()
            print_error(error)
            s.poll() # get current values
##            print getattr(s, 'dtg' )
            motion_type  =  getattr(s, 'motion_type' )
            task_mode = getattr(s, 'task_mode' )                
            print 'motion_type',motion_type,'task_mode',task_mode
            
            if motion_type == 2 and flag==0 :#0 = idle 1: Traverse 2: Linear feed 3: Arc feed 4: Tool change 5: Probing 6: Rotary axis indexing)
                c.auto(linuxcnc.AUTO_PAUSE) #run, step, pause or resume a program
                c.wait_complete() # wait until mode switch executed                     
                c.auto(linuxcnc.AUTO_RESUME) #run, step, pause or resume a program
                flag=1


    except linuxcnc.error, detail:
        print "error", detail
        sys.exit(1)

    finally:

        c.abort()