How convert a list string to a real list

[Terry Reedy]

On 11/30/2011 3:58 AM, Peter Otten wrote:
> Terry Reedy wrote:
>
>> On 11/30/2011 1:20 AM, 郭军权 wrote:
>>> Good after
>>> I have a string liststr = '["aaaa","bbbb","ccc"]' ,and I need convert it
>>> to a list like list = ["aaaa","bbbb","ccc"],what can id do?
>>
>> The easiest -- and most dangerous -- way is
>>   >>>  eval('["aaaa","bbbb","ccc"]')
>> ['aaaa', 'bbbb', 'ccc']
>>
>> But DO NOT eval unexamined strings from untrusted sources. The reason is
>> that it is much the same as letting an untrusted person sit unsupervised
>> as the keyboard of your computer with a command window open. You would
>> not want to eval
>>     "from os import system; system('<command to delete files>')"
>> where '<command...>' is replaced by something obnoxious for your
>> operating system.
>
> You can avoid these problems with ast.literal_eval():
>
> literal_eval(node_or_string)
>      Safely evaluate an expression node or a string containing a Python
>      expression.  The string or node provided may only consist of the
>      following Python literal structures: strings, numbers, tuples, lists,
>      dicts, booleans, and None.

I keep forgetting that someone thought to solve the problem of eval 
being both convinient and dangerous. Maybe if I type it once, I will 
remember.
 >>> import ast
 >>> ast.literal_eval('["aaaa","bbbb","ccc"]')
['aaaa', 'bbbb', 'ccc']

I think it would be better if safe_eval were available as an easily 
accessible builtin and dangerous_eval were tucked away in a module ;-).

-- 
Terry Jan Reedy