f_old = open("two_triangle_0001.gcode")
f_new = open("new_two_triangle_0001.gcode", "w")

for line in f_old:
    f_new.write(line)
    if 'G0 F100.000000' in line:
        f_new.write(";zdown\nG1 Z-75\n")
    
    if 'G0 F200' in line:
    	f_new.write(";zup\nG1 Z-73\n")
f_old.close()
f_new.close()