matplotlib-devel Mailing List for matplotlib

On Fri, Oct 10, 2008 at 11:31 AM, Gregor Thalhammer
<gre...@gm...> wrote:
> Is this really an intended behaviour? Wouldn't it be better if
> get_xlim() already returns a copy? Or could at least the documentation
> be updated to mention this pitfall?
I think it should return a copy -- if I don't hear any objections I'll
change it.
JDH

Dear developers,
the following example shows a somewhat unexpected behaviour of the 
get_xlim() method of an axis object: it returns a view to the internal 
data structure used to store the data limits. Because of this saving and 
restoring the data limits failed in this example (I am using matplotlib 
0.98.3):
from pylab import *
plot([0,1], [0,1]) #create some plot
ax = gca() #keep reference to axis
#after some time, I want to change the plot content, but keep the data 
limits
xlimits = ax.get_xlim() #save limits
print xlimits
ax.clear() #first clear axis, then
plot([1,2], [1,2]) #create new plot content
ax.set_xlim(xlimits) #does _not_ restore old limits
print xlimits #since saved xlimits also changed
Now I know that I have to use
xlimits = ax.get_xlim().copy()
if I want to save the data limits.
Is this really an intended behaviour? Wouldn't it be better if 
get_xlim() already returns a copy? Or could at least the documentation 
be updated to mention this pitfall?
Gregor

John Hunter wrote:
> On Wed, Oct 8, 2008 at 10:27 PM, Erik Tollerud <eri...@gm...> wrote:
>> Ah, that makes more sense Jae-Joon - thanks!
> 
> Jae-Joon -- could you handle this patch submission?
> 
> Thanks,
> JDH
Hi,
 I also had a look at this patch -- as that's a feature I was
interested in, too. There are a few things that I think need to be
changed; just want to share my thoughts:
- the parameter numpoints should be used (it's ignored right now)
- Some private variables are accessed and a new RegularPolycollection is
created (does this work eg. with a StarPolygonCollection? I haven't
checked, but I don't think so !). Instead of creating a new
RegularPolyCollection it might be more useful to make a copy of the
existing object... I was thinking about a update_from() method for the
Collection class(es) similar to update_from() for lines.
mm
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