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Date: Sat, 5 Jan 2013 15:56:31 +0000
Subject: Re: Yet another attempt at a safe eval() call
From: Oscar Benjamin <oscar.j.benjamin@gmail.com>
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Xref: csiph.com comp.lang.python:36188

On 4 January 2013 15:53, Grant Edwards <invalid@invalid.invalid> wrote:
> On 2013-01-04, Steven D'Aprano <steve+comp.lang.python@pearwood.info> wrote:
>> On Thu, 03 Jan 2013 23:25:51 +0000, Grant Edwards wrote:
>>
>> * But frankly, you should avoid eval, and write your own mini-integer
>>   arithmetic evaluator which avoids even the most remote possibility
>>   of exploit.
>
> That's obviously the "right" thing to do.  I suppose I should figure
> out how to use the ast module.

Someone has already created a module that does this called numexpr. Is
there some reason why you don't want to use that?

>>> import numexpr
>>> numexpr.evaluate('2+4*5')
array(22, dtype=int32)
>>> numexpr.evaluate('2+a*5', {'a':4})
array(22L)


Oscar