Source code for spinn_utilities.safe_eval

# Copyright (c) 2017-2018 The University of Manchester
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# the Free Software Foundation, either version 3 of the License, or
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[docs]class SafeEval(object): """ This provides expression evaluation capabilities while allowing the\ set of symbols exposed to the expression to be strictly controlled. Sample of use:: >>> import math >>> def evil_func(x): ... print("HAHA!") ... return x/0.0 ... >>> eval_safely = SafeEval(math) >>> eval_safely.eval("math.sqrt(x)", x=1.23) 1.1090536506409416 >>> eval_safely.eval("evil_func(1.23)") Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../", line 62, in eval return eval(expression, self._environment, kwargs) File "<string>", line 1, in <module> NameError: name 'evil_func' is not defined .. warning:: This is not guaranteed to be safe under all circumstances. It\ is not designed to be a fully secured interface; it just\ *discourages* abuse. """ __slots__ = ["_environment"] def __init__(self, *args, **kwargs): """ :param args:\ The symbols to use to populate the global reference table. \ Note that all of these symbols must support the `__name__`\ property, but that includes any function, method of an object, or\ module. If you want to make an object available by anything other\ than its inherent name, define it in the\ :py:meth:`eval` call. :param kwargs:\ Define the symbols with explicit names. Needed because some\ symbols (e.g., constants in numpy) do not have names that we can\ otherwise look up easily. """ env = {} for item in args: env[item.__name__] = item env.update(kwargs) self._environment = env
[docs] def eval(self, expression, **kwargs): """ Evaluate an expression and return the result. :param expression: The expression to evaluate :type expression: str :param kwargs:\ The extra symbol bindings to use for this evaluation. \ This is useful for passing in particular parameters to an\ individual evaluation run. :return: The expression result, the type of which will depend on the\ expression itself and the operations exposed to it. """ # pylint: disable=eval-used return eval(expression, self._environment, kwargs)