I am using a DC motor attached with a 2000 PPR incremental encoder. I am using RPI to count the number of ticks, my code works fine but I am not able to calculate all the 2000 ticks. Any help would be appreciated. Following is the code

import RPi.GPIO as GPIO
import time
import serial

import smbus
import time
bus = smbus.SMBus(1)
time.sleep(1)
address = 0x04


GPIO.setmode (GPIO.BCM)
GPIO.setwarnings(True)
i=0
pin_A = 17
pin_B = 18

######################################################################
def writeNumber(value):
    bus.write_byte(address, value)
    return -1

def readNumber():
    number = bus.read_byte(address)

    return number
###################################################################
Encoder_Count = 0
A_Pos2=0
GPIO.setup (pin_A, GPIO.IN)
GPIO.setup (pin_B, GPIO.IN)
A_Pos = 0
A_Last = "00"
STATE = {"0001":1,"0010":-1,"0100":-1,"0111":1,"1000":1,"1011":-1, "1101":-1, "1110":1}     

def Encoder1(channel1):
    global Encoder_Count,A_Pos,A_Last,STATE
    now = str(GPIO.input(17)) + str(GPIO.input(18))
    key = A_Last + now
    if key in STATE:
            direction = STATE[key]
            A_Last = now
            A_Pos +=direction


GPIO.add_event_detect (pin_A, GPIO.BOTH, callback=Encoder1)  
GPIO.add_event_detect (pin_B, GPIO.BOTH, callback=Encoder1)
i=0
#while(i<10):
while(1):
        print A_Pos
        time.sleep(0.01)

GPIO.cleanup()