simpleeval.py 文件源码

def __init__(self, operators=None, functions=None, names=None):
        """
            Create the evaluator instance.  Set up valid operators (+,-, etc)
            functions (add, random, get_val, whatever) and names. """

        if not operators:
            operators = DEFAULT_OPERATORS
        if not functions:
            functions = DEFAULT_FUNCTIONS
        if not names:
            names = DEFAULT_NAMES

        self.operators = operators
        self.functions = functions
        self.names = names

        self.nodes = {
            ast.Num: self._eval_num,
            ast.Str: self._eval_str,
            ast.Name: self._eval_name,
            ast.UnaryOp: self._eval_unaryop,
            ast.BinOp: self._eval_binop,
            ast.BoolOp: self._eval_boolop,
            ast.Compare: self._eval_compare,
            ast.IfExp: self._eval_ifexp,
            ast.Call: self._eval_call,
            ast.keyword: self._eval_keyword,
            ast.Subscript: self._eval_subscript,
            ast.Attribute: self._eval_attribute,
            ast.Index: self._eval_index,
            ast.Slice: self._eval_slice,
        }

        # py3k stuff:
        if hasattr(ast, 'NameConstant'):
            self.nodes[ast.NameConstant] = self._eval_nameconstant
        elif isinstance(self.names, dict) and "None" not in self.names:
            self.names["None"] = None