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copied!<p>It is possible with Ply, but requires some data massaging and token building.</p> <pre><code>import re from ply import lex tokens = ('LOOP','ASSIGNMENT') literals = '=,' re_float = r'(\d+\.\d+)' re_int = r'(\d+)' re_ident = r'([A-Za-z]\w*)' re_expr = '(%s)' % '|'.join([re_float, re_int, re_ident]) re_loop = 'DO%s%s=%s,%s' % (re_int, re_ident, re_expr, re_expr) @lex.TOKEN(re_loop) def t_LOOP(t): return t re_assignment = '%s=%s' % (re_ident, re_expr) @lex.TOKEN(re_assignment) def t_ASSIGNMENT(t): return t def t_newline(t): r'\n+' t.lineno += len(t.value) # count newlines def t_error(t): print "syntax error at %s, line# %d" % (t.value, t.lineno) DATA = """-- Spaces are ignored in FORTRAN DO 5 I=1,10 -- Loop DO 5 I=1.10 -- Assignment (DO5I = 1.10)""" def preprocess(data): re_spaces=re.compile('\s*') re_comment=re.compile('--.*$') lines = [] for line in data.split('\n'): # split into lines line = re_spaces.sub('', line) line = re_comment.sub('', line) if not line: continue # skip blank lines line = line.upper() lines.append(line) return '\n'.join(lines)+'\n' print re_assignment lexer = lex.lex() lexer.input(preprocess(DATA)) while True: tok = lexer.token() if not tok: break print tok </code></pre> <p>First, you have to manually strip comments, spaces, and force to uppercase. Then you build a parser which basically implements your grammar inline. I think it would eventually become unmanageable. If it were me, I think it would be much easier to implement my own lexer which just does line-by-line regular expression matching. All Ply's lexer really does is build one huge regular expression with all your little regular expressions and then progressively matches tokens.</p>

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