Re: [Matplotlib-users] imshow memory leak in pylab mode?

[K.-Michael A. <kmi...@gm...>]

On 2010-07-14 01:46:49 +0200, John Hunter said:

> On Mon, Jul 12, 2010 at 5:06 PM, K.-Michael Aye 
> <kmi...@gm...> wrote:
>> On 2010-07-12 23:17:19 +0200, John Hunter said:
>> 
>>> On Mon, Jul 12, 2010 at 4:06 PM, K.-Michael Aye
>>> <kmi...@gm...> wrote:
>>>> Dear all,
>>>> 
>>>> I'm not sure if this is by design or a problem:
> 
> It's by design and is not a leak.  matplotlib supports multiple images
> on the same axes, and can composite multiple images that overlap the
> same space using transparency, so each call to imshow is adding
> additional data to the axes.

Understood, and of course quite useful. But see below.

>  You can inspect the ax.images list to
> see the list of images is growing.
> 
> If you have an Image object and want to remove it from the Axes, call
> 
>   im.remove()


This worked.

> or you can manipulate the list of ax.images directly, eg
> 
>   del ax.images[0]

I tried this and got this error message:

In [10]: del ax.images.remove[0]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/Users/aye/Documents/workspace/pyrise_saver_clone/src/<ipython console> 
in <module>()

TypeError: 'builtin_function_or_method' object does not support item deletion

Here my history of that session:

1 : from fan_finder import get_data
2 : data = get_data(2)
3 : fig = figure()
4 : ax = fig.add_subplot(111)
5 : im = imshow(data)
6 : ax.images
7 : im = imshow(data)
8 : ax.images
9 : ax.images.remove[0]
10: del ax.images.remove[0]
11: hist%
12: _ip.magic("hist ")

data is a np.array


I found another funny thing:

Even so i set hold(False), and the ax.images array does not increase, 
the memory consumption increases.

I used these commands:

3 : fig = figure()
4 : ax = fig.add_subplot(111)
5 : imshow(data)
6 : ax.images
7 : hold(False)
8 : imshow(data)
9 : ax.images

At step 6 I had 1 image in the ax.images array, at step 9 still only 1, 
but RealMem went up the approx same amount between 7 and 8 then it did 
between 4 and 5.


> 
> or if you have a single image and want to update the data in it, you can do
> 
>   im = ax.imshow(something)
>   im.set_array(newdata)
I am using this way in a GUI I programmed and works very well there.


BR,
Michael

> 
> to update the array in the existing image.
> 
> JDH
> 
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