invalid literal for int() with base 10: '-f' ........ what '-f' means?

if __name__=='__main__':
    # get start and end line numbers
    start_line= float(sys.argv[1])
    end_line= float(sys.argv[2])
    #read the lines of the file and store them in a list
    data = open('pwd.txt','r')
    data_list= data.readlines()
    data.close()
    # displays lines within start to end range 
    for line in data_list[start_line:end_line]:
        print (line.strip())

Please could you let me know what is wrong with my code ? i tried both and integer but it seems like i'm all off road