On Thu, Feb 2, 2012 at 6:25 PM, Jerzy Karczmarczuk <
jerzy.karczmarc...@unicaen.fr> wrote:
> Benjamin Root on my suggestion that one can use del instead of remove :
>
> There are methods for ax that properly handle removal of types of artists
> that have been attached to an axes. The above approach assumes that no
> other collections have been plotted that you wanted to keep. The approach
> I gave is a very surgical method that makes sure that only what is supposed
> to be removed gets removed. Both are valid, and their usefulness depends
> upon which view of the data you need (remove types of artists versus
> removing particular artists).
>
> Yes, absolutely.
> With just a little remark: remove is a Python function which *searches*
> the list for a given value. del uses indices, so
> del lst[10000]
> will be most probably faster than lst.remove(value), if this value happens
> to occur for the first time at index 10000. Unless Matplotlib uses a
> specially tuned version of remove.
>
>
Don't confuse Python's remove() method for lists with the remove() method
for matplotlib Artist (and subclassed Artists) objects. Collections are a
subclass of Artist, and remove() simply means "remove me from the Axes
object I was connected to". This is because an Axes object contains lists
to the artists, collections and others that have been attached to it, and
each Artist has a reference to the Axes object that it was connected to.
So, calling remove() on an Artist will do all the appropriate house-keeping.
matplotlib Artist objects do not implement __del__(), so deleting an Artist
before calling remove() will not properly disconnect all of the callbacks
and references. I suspect that the only reason why this works at all is
that there is a lot of usage of weakrefs and it so there might be enough
error-checking to keep everything from crashing.
Others who are much more familiar with the underlying architecture may be
able to comment better. In the meantime, the pedantic, better form of:
del ax.collections[:]
would be:
for item in ax.collections :
item.remove()
del ax.collections[:]
>
>
>> Under Windows XP, ion() is not too
>> compatible with show().
>> TKAgg (by default), WXAgg and GTKAgg bomb Bens program (and without
>> draw() nothing is plotted).
>>
>>
> That would be a bug and should be reported (assuming that it is in the
> latest version). Make sure that you are using at least v1.0.1 (preferably
> v1.1.0) to make sure that show() should do what you want. Any version
> earlier than v1.0.1 is very unpredictable with respect to multiple show()
> calls.
>
> I use 1.1.0. (Python 2.7.2) I didn't report any bug because I didn't know
> whether this was a bug...
>
Then, please do report it.
> But there are more...
> The animation module uses various timers depending on the back-end. This
> is -- perhaps -- the result of the fact that Python standard Timer (a
> subclass of Thread) is, to say it mildly, rather weak. So, under Tk the
> system uses after(), wx offers its timers, etc. Timed animation works
> differently under various backends.
>
This should also be a new thread, and possibly a new bug report as well.
Ben Root
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