"""Parser for future statements """ from compiler import ast, walk def is_future(stmt):    """Return true if statement is a well-formed future statement"""    if not isinstance(stmt, ast.From):        return 0    if stmt.modname == "__future__":        return 1    else:        return 0 class FutureParser:     features = ("nested_scopes", "generators", "division",                "absolute_import", "with_statement")     def __init__(self):        self.found = {} # set     def visitModule(self, node):        stmt = node.node        for s in stmt.nodes:            if not self.check_stmt(s):                break     def check_stmt(self, stmt):        if is_future(stmt):            for name, asname in stmt.names:                if name in self.features:                    self.found[name] = 1                else:                    raise SyntaxError, \                          "future feature %s is not defined" % name            stmt.valid_future = 1            return 1        return 0     def get_features(self):        """Return list of features enabled by future statements"""        return self.found.keys() class BadFutureParser:    """Check for invalid future statements"""     def visitFrom(self, node):        if hasattr(node, 'valid_future'):            return        if node.modname != "__future__":            return        raise SyntaxError, "invalid future statement " + repr(node) def find_futures(node):    p1 = FutureParser()    p2 = BadFutureParser()    walk(node, p1)    walk(node, p2)    return p1.get_features() if __name__ == "__main__":    import sys    from compiler import parseFile, walk     for file in sys.argv[1:]:        print file        tree = parseFile(file)        v = FutureParser()        walk(tree, v)        print v.found        print