Re: [Pythoncard-users] Resource Editor bug (?)

Jussi Salmela wrote:

>Hello all and particularly Alex Tweedly, I guess!
>
>I'm using Python 2.4.3, wxPython 2.3.0, PythonCard 0.8.2 and its 
>Resource Editor on Win XP SP2.
>
>1. I have an ImageButton and a bunch of other components on my page.
>2. I enter
>    open
>into the command field of the ImageButton component in the Property Editor.
>3. I click some other component(s) active and then click ImageButton 
>active again.
>4. The command field now contains
>    <type 'file'>
>instead of the open I entered earlier.
>5. If I now run my program I get an error, so not only the display is 
>erroneous but also the resource file.
>6. If I retype open in the command field, save and run, everything works 
>as expected.
>  
>
Hmmmm - very interesting.

1. It's not unique to ImageButton - happens with any component.
2. It's (probably) not unique to the 'command' attribute - should happen 
to some others, but I haven't tried too hard to see which ones it 
happens with.

It's caused by the following snippet of code in 
modules/propertyEditor.py (and /multipropertyEditor,.py):

>         if propName not in ['label', 'stringSelection', 'text', 
> 'toolTip', 'userdata']:
>             try:
>                 value = eval(value)
>             except:
>                 pass

I'm not 100% sure why this was wanted. It does let you do interesting 
things - e.g. you can enter a string such as
   3+8
and it will be evaluated to 11 for you. You can enter a string like
  [20+3*15, 17]
and it will be evaluated (to [65,17]) for, say,  the position value. And 
various other more strange possibilities
 (e.g.   enter    self.position   and you get the current co-ords of the 
property editor window !!)

But I'm not clear on what the *useful* purpose of this eval is.

In any case, the two oddities I know about are    'open' and 'file' 
which both eval to   <type 'file'>  (though there may be others).

Suggestions (please comment):

1. short term - just avoid either open or file as command names :-)

2. figure out an exhaustive list of strings which eval to something they 
"shouldn't", and explicitly check for them (??)

3. decide that you never want to eval the user-entered value to produce 
a Python type, so add a test something like
      if not isinstance(eval(value), types.TypeType) :
before resetting the variable 'value', thus
   if propName not in ['label', 'stringSelection', 'text', 'toolTip', 
'userdata']:
            try:
                if not isinstance(eval(value), types.TypeType) : value = 
eval(value)
            except:
                pass

4. decide whether there is real purpose in doing an 'eval' here at all, 
and if there is, limiting the use to those cases, somehow.



-- 
Alex Tweedly    al...@tw...   http://www.tweedly.net



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