import ply.lex as lex
 
# List of token names
tokens = (
    'NUMBER',
    'PLUS',
    'MINUS',
    'TIMES',
    'DIVIDE',
    'IDENTIFIER',
    'KEYWORD',
)
 
# Regular expression rules for simple tokens
t_PLUS = r'\+'
t_MINUS = r'-'
t_TIMES = r'\*'
t_DIVIDE = r'/'
 
# Define a regular expression for identifying numbers
t_NUMBER = r'\d+'
 
# Define a regular expression for identifiers (names starting with a letter, followed by letters or digits)
t_IDENTIFIER = r'[a-zA-Z_][a-zA-Z0-9_]*'
 
# Define a rule for keywords
def t_KEYWORD(t):
    r'\b(if|else|while|for)\b'
    return t
 
# Define a rule for ignoring spaces and newlines
t_ignore = ' \t\n'
 
# Define a rule for handling errors
def t_error(t):
    print(f"Illegal character '{t.value[0]}'")
    t.lexer.skip(1)
 
# Build the lexer
lexer = lex.lex()
 
# Sample input string
data = '''
if x + 10 > 20:
    y = x * 2
'''
 
# Input the string to the lexer
lexer.input(data)
 
# Tokenize the input
while True:
    tok = lexer.token()
    if not tok:
        break
    print(f'Token: {tok.type}, Value: {tok.value}')

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