matplotlib-users

[Matplotlib-users] Modifying lasso_demo.py

[Scott H. <st...@co...>]

Hello, I'm trying to incorporate some matplotlib widgets into my scripts 
that generate plots. I'm unsure why, but if I wrap the figure creation 
lines in lasso_demo.py with a function the demo does not work. Why?

#Original:
#------------
if __name__ == '__main__':
     data = [Datum(*xy) for xy in randn(100,2)]
     fig = figure()
     ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
     lman = LassoManager(ax, data)
     show()

#Change:
#------------
def run(points):
     data = [Datum(*xy) for xy in points]
     fig = figure()
     ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
     lman = LassoManager(ax, data)
     show()

if __name__ == '__main__':
     points = rand(100, 2)
     run(points)


-- 
---------------
Scott T. Henderson
http://www.geo.cornell.edu/eas/gstudent/sth54/contact.html

Re: [Matplotlib-users] Modifying lasso_demo.py

[Tony Yu <ts...@gm...>]

On Wed, Jul 25, 2012 at 5:11 PM, Scott Henderson <st...@co...> wrote:

> Hello, I'm trying to incorporate some matplotlib widgets into my scripts
> that generate plots. I'm unsure why, but if I wrap the figure creation
> lines in lasso_demo.py with a function the demo does not work. Why?
>
> #Original:
> #------------
> if __name__ == '__main__':
>      data = [Datum(*xy) for xy in randn(100,2)]
>      fig = figure()
>      ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
>      lman = LassoManager(ax, data)
>      show()
>
> #Change:
> #------------
> def run(points):
>      data = [Datum(*xy) for xy in points]
>      fig = figure()
>      ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
>      lman = LassoManager(ax, data)
>      show()
>
> if __name__ == '__main__':
>      points = rand(100, 2)
>      run(points)
>
>
> --
> ---------------
> Scott T. Henderson
> http://www.geo.cornell.edu/eas/gstudent/sth54/contact.html
>

Your changes work fine on my system.

Are you sure the example you wrote above is exactly the same as what you're
running? For example, if I move the `show` out of the function and back
into '__main__', then the lasso stops working (because the lasso manager
gets garbage collected). Otherwise, I can't reproduce the issue. Actually,
what did you mean by "does not work" (e.g., no lasso, error,)?

-Tony

Re: [Matplotlib-users] Modifying lasso_demo.py

[Scott H. <st...@co...>]

Thanks for the response. To be more specific, if I run the modified script in an ipython --pylab terminal:

In [1]: %run lasso_demo.py

In [2]:

The function returns, and the lasso manager is garbage collected as you say. In other words, the plot shows up, but I can't draw a lasso and select points. If I run the script in ipython without the pylab flag it works!

Why does enabling --pylab have this effect? Since I use pylab for day-to-day computing I'd like to incorporate some of these widgit tools in interactive sessions, but maybe that's not possible?  


Thanks, 
Scott



On Jul 25, 2012, at 5:10 PM, Tony Yu wrote:

> def run(points):
>      data = [Datum(*xy) for xy in points]
>      fig = figure()
>      ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
>      lman = LassoManager(ax, data)
>      show()
> 
> if __name__ == '__main__':
>      points = rand(100, 2)
>      run(points)

Re: [Matplotlib-users] Modifying lasso_demo.py

[Eric F. <ef...@ha...>]

On 2012/07/25 12:45 PM, Scott Henderson wrote:
> Thanks for the response. To be more specific, if I run the modified
> script in an ipython --pylab terminal:
>
> In [1]: %run lasso_demo.py
>
> In [2]:
>
> The function returns, and the lasso manager is garbage collected as
> you say. In other words, the plot shows up, but I can't draw a lasso
> and select points. If I run the script in ipython without the pylab
> flag it works!
>
> Why does enabling --pylab have this effect? Since I use pylab for
> day-to-day computing I'd like to incorporate some of these widgit
> tools in interactive sessions, but maybe that's not possible?

It is entirely possible.

--pylab mode turns mpl interactive mode on, so that the call to show() 
does not block.  But because you have that call inside your function, if 
show() doesn't block, you immediately return from the function, and as 
Tony noted, your widget gets garbage-collected.

Try this: keep references to your figure and LassoManager in a list, 
dictionary, class, or whatever you like, and return that from your run() 
function.  When you call run, assign its output to a name, so there is a 
reference to it, and indirectly to the LassoManager.

Eric

>
> Thanks,
> Scott
>
>
>
> On Jul 25, 2012, at 5:10 PM, Tony Yu wrote:
>
>> def run(points):
>>       data = [Datum(*xy) for xy in points]
>>       fig = figure()
>>       ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)
>>       lman = LassoManager(ax, data)
>>       show()
>>
>> if __name__ == '__main__':
>>       points = rand(100, 2)
>>       run(points)
>
>
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