Re: make an object read only

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From	dieter <dieter@handshake.de>
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Subject	Re: make an object read only
Date	Wed, 03 Aug 2016 09:57:42 +0200
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Robin Becker <robin@reportlab.com> writes:

> A reportlab user found he was doing the wrong thing by calling canvas.save 
> repeatedly, our documentation says you should not use Canvas objects after the 
> save method has been used. The user had mixed results :(
>
> It would be better to make the canvas object completely immutable all the way 
> down when save has been called, but I think that's quite hard as these objects 
> have quite a large and varied set of attributes, lists other objects 
> dictionaries etc etc.

If changing things happen at an elementary level (by assigning to
the object's instance attributes), then you could implement
your on "__setattr__/__delattr__" methods. There, you could check
whether you are ready to allow the change or reject it.

Thread

make an object read only Robin Becker <robin@reportlab.com> - 2016-08-02 08:12 -0700
  Re: make an object read only "dfh@forestfield.co.uk" <dfh@forestfield.co.uk> - 2016-08-02 09:28 -0700
  Re: make an object read only Steven D'Aprano <steve+python@pearwood.info> - 2016-08-03 02:36 +1000
  Re: make an object read only dieter <dieter@handshake.de> - 2016-08-03 09:57 +0200
  Re: make an object read only Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-08-04 17:03 -0700
    Re: make an object read only Robin Becker <robin@reportlab.com> - 2016-08-05 09:51 +0100
    Re: make an object read only Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-08-05 11:04 +0200
    Re: make an object read only Rick Johnson <rantingrickjohnson@gmail.com> - 2016-08-07 16:40 -0700

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