# Edited for SublimeKSP: # The default divide function now uses a safe_div() function to do an interger # divide that Kontakt will understand. This means there are no floating point # numbers. # Exceptions have been removed, to be handled by the compiler instead. ''' SimpleEval - (C) 2013/2015 Daniel Fairhead ------------------------------------- An short, easy to use, safe and reasonably extensible expression evaluator. Designed for things like in a website where you want to allow the user to generate a string, or a number from some other input, without allowing full eval() or other unsafe or needlessly complex linguistics. ------------------------------------- Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ------------------------------------- Initial idea copied from J.F. Sebastian on Stack Overflow ( http://stackoverflow.com/a/9558001/1973500 ) with modifications and many improvments. ------------------------------------- Contributors: - corro (Robin Baumgartner) (py3k) - dratchkov (David R) (nested dicts) - marky1991 (Mark Young) (slicing) - T045T (Nils Berg) (!=, py3kstr, obj.attributes) ------------------------------------- Usage: >>> s = SimpleEval() >>> s.eval("20 + 30") 50 You can add your own functions easily too: if file.txt contents is "11" >>> def get_file(): with open("file.txt",'r') as f: return f.read() s.functions["get_file"] = get_file s.eval("int(get_file()) + 31") 42 For more information, see the full package documentation on pypi, or the github repo. ----------- If you don't need to re-use the evaluator (with it's names, functions, etc), then you can use the simple_eval() function: >>> simple_eval("21 + 19") 40 You can pass names, operators and functions to the simple_eval function as well: >>> simple_eval("40 + two", names={"two": 2}) 42 ''' import ast import sys import math import operator as op from random import random ######################################## # Module wide 'globals' # MAX_STRING_LENGTH = 100000 # MAX_POWER = 4000000 # highest exponent PYTHON3 = sys.version_info[0] == 3 ######################################## # Exceptions: # class InvalidExpression(Exception): # ''' Generic Exception ''' # pass # class FunctionNotDefined(InvalidExpression): # ''' sorry! That function isn't defined! ''' # def __init__(self, func_name, expression): # self.message = "Function '{0}' not defined," \ # " for expression '{1}'.".format( func_name, expression) # self.func_name = func_name # self.expression = expression # # pylint: disable=bad-super-call # super(InvalidExpression, self).__init__(self.message) # class NameNotDefined(InvalidExpression): # ''' a name isn't defined. ''' # def __init__(self, name, expression): # self.message = "'{0}' is not defined for expression '{1}'".format( # name, expression) # self.name = name # self.expression = expression # # pylint: disable=bad-super-call # super(InvalidExpression, self).__init__(self.message) # class AttributeDoesNotExist(InvalidExpression): # '''attribute does not exist''' # def __init__(self, attr, expression): # self.message = "Attribute '{0}' does not exist in expression '{1}'".format( # attr, expression) # self.attr = attr # self.expression = expression ######################################## # Default simple functions to include: def random_int(top): ''' return a random int below <top> ''' return int(random() * top) def kontakt_divide(a, b): return(int(math.copysign(abs(a) // abs(b), a / b))) ######################################## # Defaults for the evaluator: DEFAULT_OPERATORS = {ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul, ast.Div: kontakt_divide, ast.Mod: op.mod, # ast.Eq: op.eq, ast.NotEq: op.ne, ast.Gt: op.gt, ast.Lt: op.lt, # ast.GtE: op.ge, ast.LtE: op.le, ast.USub: op.neg, ast.UAdd: op.pos} DEFAULT_FUNCTIONS = {"rand": random, "randint": random_int, "int": int, "float": float, "str": str if PYTHON3 else unicode} DEFAULT_NAMES = {"True": True, "False": False} ######################################## # And the actual evaluator: class SimpleEval(object): # pylint: disable=too-few-public-methods ''' A very simple expression parser. >>> s = SimpleEval() >>> s.eval("20 + 30 - ( 10 * 5)") 0 ''' expr = "" 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 def eval(self, expr): ''' evaluate an expresssion, using the operators, functions and names previously set up. ''' # set a copy of the expression aside, so we can give nice errors... self.expr = expr # and evaluate: return self._eval(ast.parse(expr).body[0].value) # pylint: disable=too-many-return-statements, too-many-branches def _eval(self, node): ''' The internal eval function used on each node in the parsed tree. ''' # literals: if isinstance(node, ast.Num): # <number> return node.n elif isinstance(node, ast.Str): # <string> return node.s # python 3 compatibility: elif (hasattr(ast, 'NameConstant') and isinstance(node, ast.NameConstant)): # <bool> return node.value # operators, functions, etc: elif isinstance(node, ast.UnaryOp): # - and + etc. return self.operators[type(node.op)](self._eval(node.operand)) elif isinstance(node, ast.BinOp): # <left> <operator> <right> return self.operators[type(node.op)](self._eval(node.left), self._eval(node.right)) elif isinstance(node, ast.BoolOp): # and & or... if isinstance(node.op, ast.And): return all((self._eval(v) for v in node.values)) elif isinstance(node.op, ast.Or): return any((self._eval(v) for v in node.values)) elif isinstance(node, ast.Compare): # 1 < 2, a == b... return self.operators[type(node.ops[0])](self._eval(node.left), self._eval(node.comparators[0])) elif isinstance(node, ast.IfExp): # x if y else z return self._eval(node.body) if self._eval(node.test) \ else self._eval(node.orelse) elif isinstance(node, ast.Call): # function... # try: return self.functions[node.func.id](*(self._eval(a) for a in node.args)) # except KeyError: # raise FunctionNotDefined(node.func.id, self.expr) # variables/names: elif isinstance(node, ast.Name): # a, b, c... # try: #This happens at least for slicing #This is a safe thing to do because it is impossible #that there is a true exression assigning to none #(the compiler rejects it, so you can't even pass that to ast.parse) if node.id == "None": return None elif isinstance(self.names, dict): return self.names[node.id] elif callable(self.names): return self.names(node) # else: # raise InvalidExpression('Trying to use name (variable) "{0}"' # ' when no "names" defined for' # ' evaluator'.format(node.id)) # except KeyError: # raise NameNotDefined(node.id, self.expr) elif isinstance(node, ast.Subscript): # b[1] return self._eval(node.value)[self._eval(node.slice)] elif isinstance(node, ast.Attribute): # a.b.c try: return self._eval(node.value)[node.attr] except TypeError: #(KeyError, TypeError): pass # Maybe the base object is an actual object, not just a dict # try: return getattr(self._eval(node.value), node.attr) # except (AttributeError, TypeError): # pass # If it is neither, raise an exception # raise AttributeDoesNotExist(node.attr, self.expr) elif isinstance(node, ast.Index): return self._eval(node.value) elif isinstance(node, ast.Slice): lower = upper = step = None if node.lower is not None: lower = self._eval(node.lower) if node.upper is not None: upper = self._eval(node.upper) if node.step is not None: step = self._eval(node.step) return slice(lower, upper, step) else: raise FeatureNotAvailable("Sorry, {0} is not available in this " "evaluator".format(type(node).__name__ )) def simple_eval(expr, operators=None, functions=None, names=None): ''' Simply evaluate an expresssion ''' s = SimpleEval(operators=operators, functions=functions, names=names) return int(s.eval(expr))