The parser Module

(Optional) The parser module provides an interface to Pythons built-in parser and compiler.

Example 13-19 compiles a simple expression into an abstract syntax tree (AST), turns the AST into a nested list, dumps the contents of the tree (where each node contains either a grammar symbol or a token), increments all numbers by one, and, finally, turns the list back into a code object. At least thats what I think it does.

Example 13-19. Using the parser Module

File: parser-example-1.py import parser import symbol, token def dump_and_modify(node): name = symbol.sym_name.get(node[0]) if name is None: name = token.tok_name.get(node[0]) print name, for i in range(1, len(node)): item = node[i] if type(item) is type([]): dump_and_modify(item) else: print repr(item) if name == "NUMBER": # increment all numbers! node[i] = repr(int(item)+1) ast = parser.expr("1 + 3") list = ast.tolist() dump_and_modify(list) ast = parser.sequence2ast(list) print eval(parser.compileast(ast)) eval_input testlist test and_test not_test comparison expr xor_expr and_expr shift_expr arith_expr term factor power atom NUMBER 1 PLUS + term factor power atom NUMBER 3 NEWLINE \ ENDMARKER \ 6