[Tutor] what is the meaning of variable e

[Dave Angel]

On 04/26/2013 01:45 AM, wang yong wrote:
> Hi tutors,
>
> I am a newb. Please bear with my simple question.

If you're new to Python, then any GUI question isn't "simple."  But 
perhaps you're not new to Python, but only to PyQT.  I'll qualify my 
remarks with the statement that I'm not familiar with PyQt, but I am 
with GUI's in general.  So I hope I can help.

  Please refer to the code
> as following. The question is: what is the special meaning of 'e' variable
> in the class of 'Button'.

'e' is not special to the class at all.  It's just a parameter specified 
in two of the class methods.  So somebody makes a call something like:
     context =    --instance of some class that has a mimeData method--
     mybutton.dragEnterEvent(context)


The second one is how function 'dragEnterEvent'
> and 'dropEvent' got executed with calling from class 'example'. Thanks a
> lot for the help.

By making your Button class a child of  QtGui.QPushButton, you inherit a 
lot of behavior.  Apparently two pieces of that is the binding of these 
two methods to the button.  Whenever somebody calls a method on 
QtGui.QPushButton that you have also defined, they end up calling your 
version instead of the default one in the base class.

Apparently, when a user does a drag-drop targeting a QPushButton, it 
fires one or both of those events.

For more details, you need to ask someone who knows PyQt.  I don't see 
it discussed here very much, so you'd probably be better off with the 
docs, or on a PyQt forum.



-- 
DaveA