Invalid 'api_key' or 'access_token'

from kiteconnect import KiteTicker,KiteConnect
import pandas as pd
from datetime import datetime, timedelta
import talib

if __name__ == '__main__':
    api_key=open('api_key.txt','r').read()
    api_secret = open('api_secret.txt','r').read()

    kite = KiteConnect(api_key=api_key)

    access_token = open('access_token.txt', 'r').read()

    kite.set_access_token(access_token)

    # print(kite.login_url())
    # data = kite.generate_session("p0g6JdwUlrEqBAyruSTBfynE512nJULK", api_secret=api_secret)
    # print(data['access_token'])
    # kite.set_access_token(data['access_token'])
    # with open('access_token.txt', 'w') as ak:
    #     ak.write(data['access_token'])
    #
    #

    # # Dates between which we need historical data
    from_date = datetime.strftime(datetime.now() - timedelta(100), '%Y-%m-%d')
    to_date = datetime.today().strftime('%Y-%m-%d')

    # Interval(minute, day, 3 minute, 5 minute...)
    interval = "5minute"
    current_signal = ''
    tokens = {738561: 'RELIANCE', 341249: 'HDFCBANK'}

#following line  is just to check if kite,place_order is working or not

                kite.place_order(tradingsymbol=tokens[token], variety="REGULAR",exchange="NSE", quantity=1, transaction_type="BUY",order_type="MARKET", product="CNC")

    while True:
        # if (datetime.now().second == 0) and ((datetime.now().minute) % 5 == 0):
            for token in tokens:
                records = kite.historical_data(token,from_date=from_date,to_date=to_date,interval=interval)
                df = pd.DataFrame(records)
                df.drop(df.tail(1).index, inplace=True)
                # print(df)
                open = df['open'].values
                high = df['high'].values
                low = df['low'].values
                close = df['close'].values
                volume = df['volume'].values

                sma5 = talib.SMA(close,5)
                sma20 = talib.SMA(close,20)
                print(sma5[-1])
                print(sma20[-1])

#following line  is just to check if kite,place_order is working or not

                kite.place_order(tradingsymbol=tokens[token], variety="REGULAR",exchange="NSE", quantity=1, transaction_type="BUY",order_type="MARKET", product="CNC")

#actual buy and sell logic
                if (sma5[-2] < sma20[-2]) and (sma5[-1] > sma20[-1]):
                    buy_order_id = kite.place_order(tradingsymbol=tokens[token], exchange="NSE", quantity=1,transaction_type="BUY", order_type="MARKET", product="CNC")
                    # current_signal = 'buy'

                if (sma5[-2] > sma20[-2]) and (sma5[-1] < sma20[-1]):
                    sell_order_id = kite.place_order(tradingsymbol=tokens[token], exchange="NSE", quantity=1,transaction_type="SELL", order_type="MARKET", product="CNC")
                    # current_signal = 'sell'

1759.3900000000133
1750.2950000000012
Traceback (most recent call last):
  File "C:/Users/My/PycharmProjects/bhavcopy/zerodha_strategy.py", line 54, in <module>
    kite.place_order(tradingsymbol=tokens[token], variety="REGULAR",exchange="NSE", quantity=1, transaction_type="BUY",order_type="MARKET", product="CNC")
  File "C:\Users\My\AppData\Local\Programs\Python\Python37\lib\site-packages\kiteconnect\connect.py", line 346, in place_order
    return self._post("order.place", params)["order_id"]
  File "C:\Users\My\AppData\Local\Programs\Python\Python37\lib\site-packages\kiteconnect\connect.py", line 821, in _post
    return self._request(route, "POST", params)
  File "C:\Users\My\AppData\Local\Programs\Python\Python37\lib\site-packages\kiteconnect\connect.py", line 886, in _request
    raise exp(data["message"], code=r.status_code)
kiteconnect.exceptions.InputException: Invalid `api_key` or `access_token`.