[chimera-dev] [Chimera-users] Programmer's Guide feedback....

[Eric Pettersen]

On Dec 15, 2009, at 9:36 AM, Tom Goddard wrote:

>   4. The ToolbarButton.py doesn't work unless the "import re" and  
> "import chimera" are in the function body.  This is because Chimera  
> deletes all globals after loading a file.  This has often been a  
> headache for me and Chimera should not delete globals.

This is a behavior of Python.  We load scripts into their own  
temporary module to avoid pollution of the Chimera main namespace  
(e.g. if the script defined globals named "id" or "sum" or "type" they  
would override built-in functions of the same name for all future  
script executions!).  When Chimera unloads the temporary module,  
Python nulls out it's global namespace (to give garbage collection a  
shot at working).

Now perhaps Chimera shouldn't unload the module.  I think this would  
be a reasonable change.  Perhaps it could be discussed at our next  
internal Chimera developers' meeting to ensure that I'm not forgetting  
any other ramifications that the change might have.

--Eric

                         Eric Pettersen
                         UCSF Computer Graphics Lab
                         http://www.cgl.ucsf.edu


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