python is

def get_char():
    global character_class
    global next_char
    global fp

    next_char = fp.read(1)
    if next_char.isalpha():
        character_class = LETTER
    elif next_char.isdigit():
        character_class = DIGIT
    else:
        character_class = UNKNOWN


def get_non_blank():
    while next_char.isspace():
        get_char()

# Constants
# Character Classes
LETTER = 0
DIGIT = 0
UNKNOWN = 99

# Token Codes
INT_LIT = 10
IDENT = 11
ASSIGN_OP = 20
ADD_OP = 21
SUB_OP = 22
MULT_OP = 23
DIV_OP = 24
LEFT_PAREN = 25
RIGHT_PAREN = 26

# Initialize Global Variables
character_class = -1
lexeme = -1
next_char = -1
lex_length = -1
token = -1
next_token = -1

# Get the name of the input file from the user.
file_name = input("Input file name: ")

# Open the file and read the first char.
# NOTE: error handling needs to be added later.
try:
    with open(file_name, "r") as fp:
        get_char()
        while next_char:
            print(next_char)
            get_non_blank()
except OSError:
    print("Unable to open file")
    quit()