Using evdev for background script

[hotcocoa]

What I'm attempting to do is have a python script running in the background at all times that only takes input from one of the usb devices plugged into the Raspberry Pi, in this case, it's a barcode scanner. What I've gotten so far works really well, but here's what's missing. I don't want that input to "show up" anywhere. I want the script to handle it and then make it go away.

Here's what I've got, in case anyone's interested:

Any help is appreciated in advance!

import evdev
from evdev import ecodes
import RPi.GPIO as GPIO
import time
from datetime import datetime

SCANCODES = { 
    # Scancode: ASCIICode 
    0: None, 1: u'ESC', 2: u'1', 3: u'2', 4: u'3', 5: u'4', 6: u'5', 7: u'6', 8: u'7', 9: u'8', 
    10: u'9', 11: u'0', 12: u'-', 13: u'=', 14: u'BKSP', 15: u'TAB', 16: u'q', 17: u'w', 18: u'e', 19: u'r', 
    20: u't', 21: u'y', 22: u'u', 23: u'i', 24: u'o', 25: u'p', 26: u'[', 27: u']', 28: u'CRLF', 29: u'LCTRL', 
    30: u'a', 31: u's', 32: u'd', 33: u'f', 34: u'g', 35: u'h', 36: u'j', 37: u'k', 38: u'l', 39: u';', 
    40: u'"', 41: u'`', 42: u'LSHFT', 43: u'\\', 44: u'z', 45: u'x', 46: u'c', 47: u'v', 48: u'b', 49: u'n', 
    50: u'm', 51: u',', 52: u'.', 53: u'/', 54: u'RSHFT', 56: u'LALT', 57: u' ', 100: u'RALT' 
}

in1 = 16
in2 = 18

GPIO.setmode(GPIO.BOARD)
GPIO.setwarnings(False)
GPIO.setup(in1, GPIO.OUT)
GPIO.setup(in2, GPIO.OUT)

GPIO.output(in1, True)
GPIO.output(in2, True)

mem_num = ""
valid_card = False
mem_file = open("/home/verhovay/Programs/members.txt", "r")
mem_list = mem_file.readlines()
mem_file.close()

def read_keys(device):
    obj = evdev.InputDevice(device)
    for x in obj.read_loop():
        if x.code in SCANCODES and x.type == ecodes.EV_KEY and x.value == 1:
            yield SCANCODES[x.code]
            
def inputesque(what):
    s = []
    for x in what:
        if x == 'CRLF':
            break
        s.append(x)
    return "".join(s)

def LogEntry( mNum, Valid ):
    today = datetime.today()
    now = datetime.now()
    dateCap = today.strftime("%Y-%m-%d")
    timeCap = now.strftime("%H:%M:%S")
    targetFolder = "/home/verhovay/Programs/Logs/" + dateCap + ".txt"
    target = open(targetFolder, 'a')
    if Valid:
        target.write(timeCap + " => " + mNum + " => Valid \n")
    else:
        target.write(timeCap + " => " + mNum + " => Invalid \n")
    target.close()
    return

while True:
    try:
        mem_num = inputesque(read_keys("/dev/input/by-id/usb-SM_SM-2D_PRODUCT_HID_KBW_APP-000000000-event-kbd"))
        if mem_num == "1":
            break
        valid_card = mem_num.startswith("LSHFTvLSHFThLSHFTa100") or mem_num.startswith("LSHFTvLSHFThLSHFTa200")
        mem_num = str(mem_num.replace("LSHFTvLSHFThLSHFTa100", ""))
        mem_num = str(mem_num.replace("LSHFTvLSHFThLSHFTa200", ""))
        if (mem_num + "\n") in mem_list and valid_card:
            LogEntry (mem_num, True);
            GPIO.output(in1, False)
            GPIO.output(in2, False)
            time.sleep(.5)
            GPIO.output(in1, True)
            GPIO.output(in2, True)
        else:
            LogEntry (mem_num, False);
            print("Not Valid")
            
    except Exception as err:
        now = datetime.now()
        dt_string = now.strftime("%d/%m/%Y %H:%M:%S")
        print (err, "***", dt_string)

[hotcocoa]

I figured it out. Looks like I can't delete a post, so I may as well provide the answer. To get exclusive access to a device, the following code worked well:

from evdev import ecodes, InputDevice
dev = InputDevice('/dev/input/by-id/[deviceID]')
dev.grab()

...and to release exclusive access...

dev.ungrab()

Simple enough!