Re: [Matplotlib-users] Using blit=True in matplotlib.animation

[Thomas C. <tca...@gm...>]

Please keep discussion on the list.

That warning means some thing is importing pyplot before your file. You
need to make sure that you use `matplotlib.use` before anything in your
process import `pyplot`.

You may need to change your `matplotlibrc` file.

Tom

On Sun, May 31, 2015, 00:30 Peter Rowat <pe...@pe...> wrote:

> My file starts:
> import numpy as np
> import matplotlib
> matplotlib.use('TKAgg')
> import matplotlib.pyplot as plt
> import matplotlib.animation as animation
>
>
> and the animation works, with blit=False, but with this message:
> ======
> /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/__init__.py:1155:
> UserWarning:  This call to matplotlib.use() has no effect
> because the backend has already been chosen;
> matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
> or matplotlib.backends is imported for the first time.
>
>   warnings.warn(_use_error_msg)
> =======
> So I can live with this, but seems there is something not quite right
> about the __init__.py code
> Should I use a different backed than the OS X backend?
>
> — Peter
>
> On May 30, 2015, at 8:43 PM, Thomas Caswell <tca...@gm...> wrote:
>
> Blitting not working for the osx backend is a long standing issue due to
> differences between what is allowed in the different gui frame works.
>
> You have to change the backend via `use` before you import pyplot.  If you
> are still getting the error it is likely you tried to change the backend
> _after_ pyplot was imported, in which case the `use` command does nothing.
>
> Tom
>
> On Sat, May 30, 2015 at 11:03 PM Peter Rowat <pe...@pe...>
> wrote:
>
>> I’m on OS X, trying to write a multi-slider-controlled animation. If I
>> have blit=True in the call to matplotlib.animation,
>> I get this message
>>
>> matplotlib.animation.BackendError: The current backend is 'MacOSX'
>> and may go into an infinite loop with blit turned on.  Either
>> turn off blit or use an alternate backend, for example, like
>> 'TKAgg', using the following prepended to your source code:
>>
>> import matplotlib
>> matplotlib.use('TKAgg’)
>> =====
>>
>> When I make this change  I still get the same error message, whether blit
>> is set True or False.
>> At least when blit=False the animation runs, which I can live with for
>> the moment.
>>
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>
>