Calc1, Python 3 - rextester

Calc1

#python 3.6.9

# ------------------------------------------------------------
# calclex.py
#
# tokenizer for a simple expression evaluator for
# numbers and +,-,*,/
# ------------------------------------------------------------
import ply.lex as lex
 
# List of token names.   This is always required
tokens = (
    'NUMBER',
    'PLUS',
    'MINUS',
    'TIMES',
    'DIVIDE',
    'LPAREN',
    'RPAREN',
    'MODULO',
)
 
# Regular expression rules for simple tokens
t_PLUS    = r'\+'
t_MINUS   = r'-'
t_TIMES   = r'\*'
t_DIVIDE  = r'/'
t_LPAREN  = r'\('
t_RPAREN  = r'\)'
t_MODULO = r'\%'
 
# A regular expression rule with some action code
def t_NUMBER(t):
     r'\d+'
     t.value = int(t.value)    
     return t
# Define a rule so we can track line numbers
def t_newline(t):
     r'\n+'
     t.lexer.lineno += len(t.value)
 
# A string containing ignored characters (spaces and tabs)
t_ignore  = ' \t'
 
# Error handling rule
def t_error(t):
     print("Illegal character '%s'" % t.value[0])
     t.lexer.skip(1)
 
# Build the lexer
lexer = lex.lex()

# --- Probar el lexer construido
data = '''
 3 + 4 * 10
   + -20 *2
   % 4
 '''
lexer.input(data)
# Tokenize
while True:
     tok = lexer.token()
     if not tok: 
         break      # No more input
     print(tok)


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