On Thu, May 2, 2019, 9:24 PM Zhen Huang <qeejiw...@gmail.com> wrote:
> Hi ,
>
> I have a question about python build-in function 'eval ' , please check
> out the example code below :
>
> ## create a polySphere , default name : 'pSphere1'
>
> import pymel.core as pm
> from pymel.core import nt
>
> # initialize a pymel transform node
> pymelShpere = pm.PyNode('pSphere1')
> # put it to a dict
> testDict = {0:pymelShpere}
> # convert it to str which can be stored as string in file basic data
> strMark = str(testDict)
>
> # now read it back , if scene has the pShere1 , it will work perfectly
> newDict = eval(strMark)
>
> # now delete the pShpere1 , and try to convert data to dict , failed
> because the pymel nt will try to initialize the string 'pShere1' to pymel
> node
> newDict =eval(strMark)
>
>
> My question : if I have lots of nodes store in a string data which convert
> from dict , is there a way to just make it out , just ignore error part or
> if node not exists it just convert from nt to string name ?
> if pSphere2 not exist then return
>
> {0:nt.Transform('pSphere1'), 1:'pSphere2' }
>
>
>
> Any idea is very much welcome , big thanks !!!
>
I would advise staying away from the eval() approach. Not only is it going
to be inflexible for your current goal, it also can cause unwanted
execution of arbitrary logic. A random code snippet that deletes files
could be set on a node and your code would blindly execute it as your own
user. You don't want random code being evaluated like that.
A better approach would be to use a proper serialisation format like json
or pickle (protocol version 1 for ascii format). This would allow you to
read the data back into a dictionary and then evaluate each value and
filter what does and does not exist in the scene.
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