[reportlab-users] get methods for properties

Robin Becker reportlab-users@reportlab.com
Fri, 11 Jun 2004 09:01:15 +0100

Randall Smith wrote:

> I'm new to reportlab.  I've been playing with it and looking at the 
> source.  I like the design, especially the templates.  Thank you for 
> opening it to the public; I hope you get useful feedback.
> My comment is about getting properties.  Maybe I missed it, but I don't 
> see a clean way to grab some useful properties.  For example, line 
> width.  I wrote a flowable to draw a horizontal line.  I want to set the 
> line width and return it back to what it was before the flowable was 
> created.  Because _lineWidth starts with a _, I'm guessing this is a 
> semi-private variable and subject to change (not part of the API).  So 
> shouldn't canvas have an API attribute or call like canvas.lineWidth or 
> canvas.getLineWidth()?
> Here is code below:
> class HR(Flowable):
>     def __init__(self, height):
>         Flowable.__init__(self)
>         self.height = height
>     def __repr__(self):
>         return "HR(t=%s)" % (self.height,)
>     def draw(self):
>         orig_linewidth = self.canv._lineWidth # my problem is here
>         self.canv.setLineWidth(height)
>         self.canv.line(0, 0, 100, 0)
>         self.canv.setLineWidth(orig_linewidth)
> Randall

I don't thinks there's anything wrong with reading _lineWidth and 
friends, but the _ indicates it shouldn't be set. In modern Python we 
could use a property to allow reading and writing with the appropriate 
methods called on the underlying _ value.

On the other hand the platypus/flowables framework allows you to make 
any changes you like in your draw method. Each call to a draw method is 
surrounded by a save & restore so you can feel free to do what you like 
to the canvas inside. That means you don't need to save the linewitdh 

Robin Becker