User defined M-code calling python script

$ #---------------------------------------------------------------
$ # Start in the directory for the axis sim:
$ cd configs/sim/axis 
$ #---------------------------------------------------------------
$ # Copy axis.ini:
$ cp axis.ini tst.ini
$ #---------------------------------------------------------------
# Edit tst.ini for explicit specification for M file location:
$ gedit tst.ini 
#---------------------------------------------------------------
# Show explicit specification for M file location:
$ grep -2 USER_M_PATH tst.ini

[RS274NGC]
USER_M_PATH = .


$ #---------------------------------------------------------------
$ # Show the M102 file:
$ cat ./M102
#!/bin/bash
echo "this is $0"
./a.py &
echo "started a.py in background"
exit 0
$ 
$ #---------------------------------------------------------------
$ # Show the python file (a.py):
$ cat ./a.py
#!/usr/bin/python
def bcmd():
    print 'hellooooooooo'

import Tkinter
rw = Tkinter.Tk()
b  = Tkinter.Button(rw,text="Hello",command=bcmd)
b.pack()
rw.mainloop()
$ 
$ #---------------------------------------------------------------
$ # make sure both files are executable:
$ chmod +x ./M102
$ chmod +x ./a.py
$ 
$ #---------------------------------------------------------------
$ # test simulator tst.ini
$ linuxcnc ./tst.ini &
   ...
   F1,F2, Home All, MDI tab, Run M102:

this is ./M102  
started a.py in background

   ...
   Push the Hello button 
hellooooooooo

#!/bin/bash
# file to engage camera piston
halcmd setp parport.1.pin-17-out False
~/linuxcnc/configs/DVDCNC1/mcodes/camera1.py
exit 0

#!/usr/bin/python
"""
requires: python-opencv 

"""
import cv2

#required for rotation transform
import numpy as np


camera_number = 0 #0, 1, x..

white = 255,255,255
black = 0,0,0
red = 0,0,255
green = 0,255,0
blue = 255,0,0

#constants
rot_angle = 90 #Angle to rotate image by
color_line = blue #lines and circles color
scale = 1
x_offset=0	#offset between camera and spindle
y_offset=20	#offset between camera and spindle

#captures video from 0
cap = cv2.VideoCapture(camera_number)
ret, frame = cap.read()		#capture the first frame to determine size
img1 = frame		  	#rename frame before transformations
# find the orginal height and width of the image (output is a tuple)
rows, cols, depth = img1.shape
#print rows, cols, depth
# Get rotation matrix getRotationmatrix2D(center,angle,scale)
M = cv2.getRotationMatrix2D((cols/2,rows/2),rot_angle,scale)


while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()
    #ret = cap.set(3,640)
    #ret = cap.set(4,480)

    # calculate rotated image warpAffine(input image,output image,trans matrix,output size)
    img_rotated = cv2.warpAffine(frame,M,(cols,rows))

    # add lines and circles to the captured frame
    cv2.line(img_rotated,(0,(240-y_offset)),(640,(240-y_offset)),(color_line),1)
    cv2.line(img_rotated,((320+x_offset),0),((320+x_offset),480),(color_line),1)

    cv2.circle(img_rotated,((320+x_offset),(240-y_offset)), 20, (color_line), 1)
    cv2.circle(img_rotated,((320+x_offset),(240-y_offset)), 50, (color_line), 1)
    cv2.circle(img_rotated,((320+x_offset),(240-y_offset)), 90, (color_line), 1)
    cv2.circle(img_rotated,((320+x_offset),(240-y_offset)), 130, (color_line), 1)
    cv2.circle(img_rotated,((320+x_offset),(240-y_offset)), 170, (color_line), 1)
    cv2.rectangle(img_rotated,(0,450),(80,480),(0,0,0),-1)
    font = cv2.FONT_HERSHEY_SIMPLEX
    cv2.putText(img_rotated,'[q]uit',(10,470), font, 0.7,(255,255,255),1)
    #cv2.putText(img_rotated,'[q]uit    [a]circle+ [z]circle-    [c]olor',(10,470), font, 0.7,(255,255,255),1)

    # shows final image imshow(window_name,target_image)
    cv2.imshow('DVD CNC Camera', img_rotated)

    # wait for input keys
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()